Messaging Service could not be attached to the Campaign because Twilio's DCA declined the Campaign due to compliance violations.
Possible Causes
Twilio identified compliance violations during the review process. The specific reason for rejection is provided in the CAMPAIGN_SHARE_DELETE webhook from TCR.
Possible Solutions
Revise the Campaign details to address the compliance issues and re-share the Campaign with Twilio's DCA for another review.
For further clarification and resolution, contact Twilio Customer Support.