The "expired but won't reconnect" issue is usually a ghost connection stuck on Facebook's side. Refreshing permissions inside ManyChat won't clear it. Try this full reset:
1. Facebook Business Settings → Integrations → Connected apps → find ManyChat → Remove
2. Personal Facebook profile → Settings → Business Integrations → find ManyChat → View and edit → Remove (this is the one people miss)
3. Instagram → App Website Permissions → Apps and websites → Active → remove ManyChat if still there
4. Instagram → Settings → Messages and story replies → Message requests → Connected tools → make sure "Allow access to messages" is ON
5. Check handover protocol: FB Page → Advanced messaging → Handover protocol → primary receiver = ManyChat
6. Clear browser cache, then reconnect from ManyChat
If it still shows expired after all that, only ManyChat support can reset it on their backend, the forum can't unstick it.