Summary: When a message fails to send, you can hover over the failed to send indicator to see the specific error. This article explains what each error means and what steps you can take to resolve it.
Permissions Required: Converser
Error Messages:
"This message was not delivered to maintain a healthy ecosystem" (WhatsApp channel)
This is a Meta restriction applied to marketing message templates. Meta enforces limits on certain outbound marketing messages to reduce spam and protect users from unsolicited communications. When this threshold is reached, the message is blocked at the platform level.
Common triggers:
The same marketing template is being sent to a large number of guests in a short period of time
Your WhatsApp Business number's quality rating has dropped due to guests reporting messages as spam
The volume of outbound marketing messages exceeds Meta's per-number limits
What you can do:
Avoid sending the same template to many guests simultaneously
Space out outbound marketing messages over time rather than bulk-sending
Ask your AXP administrator to check your number's quality rating in Meta Business Manager → WhatsApp Manager → Phone Numbers
If the rating is Yellow or Red, follow the recommendations shown in Meta Business Manager to recover it
"Destination is invalid" or "Message failed to send because the user is unreachable" (All channels)
The message could not be delivered because the destination phone number is incorrect, unreachable, or restricted.
Common triggers:
The phone number has a missing, extra, or incorrect digit
The country code is wrong or missing
The guest's device is switched off or out of service at the time the message was sent
The guest's mobile provider is out of service temporarily
Regional SMS regulations restrict messaging between certain countries (e.g. some international routes are blocked by carriers)
The number is a landline rather than a mobile number
What you can do:
Double-check the guest's phone number against their PMS profile — look for extra digits, missing digits, or an incorrect country code
If the number appears correct, try again later in case the guest's device was temporarily out of service
If the number is a landline, SMS cannot be delivered to it — contact the guest via a different channel or update the guest's primary number to mobile number if you have it
If the issue is cross-country SMS routing, note that AXP maintains both US and UK sender numbers on locations to mitigate common regional restrictions — contact the Alliants Support team via Help & Support → Live Chat if you believe a routing issue is affecting your location
💡 Tips: To find other channels the guest has used previously, go to the guest's profile → Operations → Conversations and reopen a conversation from there.
"The phone number provided is not registered with WhatsApp" (WhatsApp channel)
or
The guest's number is not associated with a WhatsApp account. WhatsApp messages can only be delivered to numbers that have an active WhatsApp account registered.
Common triggers:
The guest does not use WhatsApp
The guest recently changed their phone number and the new number is not registered with WhatsApp
The number belongs to a device that does not support WhatsApp
What you can do:
Do not attempt to resend via WhatsApp — it will continue to fail
Open the guest's profile → Operations → Conversations to see which channels the guest has previously used
Reopen the conversation from a channel that has worked before (e.g. email, SMS, or in-app messaging)
"Message cannot be sent with the current combination of To and/or From parameters" (SMS channel)
This often happens to SMS channel. It is a Twilio error (code 21612) indicating that the sender number and recipient number are in incompatible countries. SMS messaging between certain country combinations is restricted at the carrier level.
Common trigger 1 :
A US sender number (+1) is being used to message a guest with a UK number (+44). Your location only has a US number configured but the guest is in a country that requires a local sender number.
What you can do:
This cannot be resolved by resending — the sender/recipient country combination is incompatible
Contact the Alliants Support team via Help & Support → Live Chat to request a UK (or appropriate country) sender number be configured for your location
Alternatively, speak to your Success Manager to discuss adding a local number
🗒️Info: See Twilio error 21612 for more technical detail on this restriction.
Common trigger 2 :
A non-local sender number (e.g. US +1) is used to message a guest in a country where international long codes are entirely unsupported by carriers — for example, UAE (+971), where domestic long codes, international long codes, and short codes are all blocked at the carrier level, and only a pre-registered Alphanumeric Sender ID is permitted
What you can do:
This cannot be resolved by resending — the sender/recipient country combination is incompatible
To diagnose routing issues for any country combination, visit twilio.com/en-us/guidelines/[ISO-code]/sms using the destination country's ISO code (e.g.
/ae/smsfor UAE,/gb/smsfor UK). In the Long codes and short codes table, if "Long code international" shows "Not Supported", no non-local sender can route to that country. Where only a pre-registered Alphanumeric Sender ID is available, contact Alliants Support to discuss that option via Help & Support → Live Chat.Alternatively, speak to your Success Manager to discuss this issue.
"The Messaging Service Contains No Phone Numbers" (SMS channel)
This is a Twilio error (code 21704) that occurs when the SMS messaging service assigned to the property has no sender phone numbers configured. In AXP, you may also see the error message when hoovering under the 'Failed to send':
Common triggers:
The property does not have an active Twilio number assigned to their messaging service
The SMS integration is still connected in but the underlying Twilio messaging service pool is empty
What you can do:
Do not attempt to resend via SMS — it will continue to fail until a sender number is provisioned
If the guest's last active channel was SMS, use an approved proactive WhatsApp template to re-open the conversation on a working channel
Ask your brand admin to contact the Alliants Support team via Help & Support → Live Chat to raise a Change Request to have the SMS integration be disabled for the property if SMS is not part of your package
ℹ️ Info: See Twilio error 21704 for more technical detail on this error.
"The guest has opted to block further messages" (SMS & WhatsApp channels)
The guest has blocked your number and will no longer receive messages from it.
Common triggers:
The guest's number is unverified and they are avoiding unsolicited messages
The guest previously marked a message from your number as spam
The guest manually blocked your WhatsApp or SMS number
What you can do:
You cannot unblock the number from AXP — the guest must unblock it from their own device
If appropriate, contact the guest via a different channel to let them know and ask them to unblock your number
If the block appears unintentional, the guest can go to their WhatsApp contacts, find your business number, and choose Unblock
"Message failed to send because either the recipient never messaged the sender number, or more than 24 hours have passed since the recipient last replied" (WhatsApp channel)
WhatsApp only allows free-form messages within a 24-hour window of the guest's last inbound message. Outside of this window, the conversation is locked and only approved proactive templates can be used to re-open it.
Common triggers:
The guest has not replied in more than 24 hours
A staff member is following up on an older conversation without checking the timestamp
The guest initiated the conversation on a different sender number than the one being used to reply
What you can do:
Check the timestamp of the guest's last inbound message
If more than 24 hours have passed, do not type a free-form reply — it will fail
Select an approved proactive WhatsApp template to re-open the conversation
Once the guest replies, the 24-hour window resets and free-form messages can be sent again
⚠️ Alert: Any change to the content of a proactive template — even a minor edit — will cause the template to fail until it has been resubmitted to Meta for approval. Location admins and brand admins can edit templates, but changes must be approved by Meta before use.
You can submit it for approval on your Meta business portal if you have access, otherwise, please speak to Alliants Support team for assistance.
"Message could not be delivered for an unknown reason. Please try again and if the problem persists, contact our support team" (WhatsApp channel)
This is a generic fallback error returned when WhatsApp cannot provide a specific failure code. It covers several distinct causes that require further investigation.
Common triggers:
A WhatsApp template was recently edited but the updated version has not been submitted to Meta for approval
The template is categorised as Marketing and is being sent to a US or Canadian (+1) number — Meta blocks marketing templates to +1 number
The guest's Sunshine Conversations profile has been merged with another profile sharing the same phone number, making the original messaging ID invalid.
A transient error on Meta's or Sunshine Conversations' infrastructure a retry usually helps to resolve this
What you can do:
Check whether a template was used — if so, confirm with your Location or Brand admin that the template has not been recently edited without resubmission to Meta
Check the template category in your Meta Business portal — if it is Marketing, it cannot be sent to +1 numbers; switch to a Utility template. If you don't have access to your Meta Business portal, contact Alliants Support team to check logs
If the message was free-typed and the window is still open, wait a few minutes and try again — transient errors usually resolve on retry
If the problem persists, contact the Alliants Support team via Alliants Platform > Help & Support → Live Chat so they can check delivery error logs and investigate further
🗒️ Info: For more WhatsApp message fail to send causes, see also: Why can't I send an outbound WhatsApp message to a guest phone number?
"Message could not be delivered for an unknown reason" (Facebook Messenger channel)
If this error appears alongside a Facebook Messenger logo, the cause is different — the Facebook Messenger channel integration has broken and needs to be reconnected.
Common triggers:
The Facebook page admin changed their Facebook password or security settings, disconnecting the integration
The Facebook page access token has expired
The page's Messenger settings were changed in Meta Business Suite
What you can do:
This cannot be resolved from within AXP — the Facebook page admin must re-integrate the channel from within your Facebook tool.
Share the following guide with the relevant Facebook page admin: Why is Facebook Messenger not delivering messages?
Common Questions
Q: Where do I find the error message for a failed send?
A: In the Conversations module, hover over the failed to send indicator under the message. The specific error text will appear in a tooltip.
Q: Can I resend a failed message?
A: It depends on the error. Transient errors (unknown reason) are worth retrying after a few minutes. Errors caused by an invalid number, a blocked guest, or a template restriction will continue to fail until the underlying issue is resolved.
Q: Who do I contact if I cannot resolve the error myself?
A: Contact the Alliants Support team via Help & Support → Live Chat in the AXP app. Include the guest's name, the conversation link, and the error message you are seeing.