Sorry for the late response, just spotted this error again:
POST https://zoom.us/v2/im/chat/messages
{"account_id":"vCpAgfHuRDeDglOT3J1tFQ","to_jid":"-d8wpkcbs7otk5l4groq7q@xmpp.zoom.us","content":{"head":{"text":"test"}},"robot_jid":"v1d97h7pq_rp-r9urflxqzzw@xmpp.zoom.us"}
For most users, this does work… but not for this one…
He did not uninstall the app. I checked the token is working was able to make requests with it to retrieve meeting and user objects. Also my webhooks are subscribed to uninstalls and deauthorizations