Troubleshooting FB Messenger connection
What do do when Facebook Messenger messages cannot be delivered?
Your Facebook Messenger integration (access token) can become invalid for a variety of reasons. Typically, this happens when a Facebook administrator changes his/her Facebook password. - this will make Facebook revoke all current app permissions.
To solve this, you will have to re-assign the Facebook Page again (re-create the integration) to provide the integration with a new token. Unfortunately we can't do this ourselves because it requires your Company´s FB administrator to be logged into Facebook Business section.
- Delete the current integration.
- Create the integration again
While/after being logged-in at Facebook (as an admin of the page you want to connect)