This isn’t a flow or permission issue. The AADSTS50013 / invalid_grant error means the Microsoft Bookings connector can’t acquire an on‑behalf‑of token from Entra ID, so it can’t even list booking pages.
The App ID in the error is Microsoft‑owned, so rotating keys or changing Azure AD settings won’t help. When this happens, the trigger shows “Invalid parameters” and the flow can’t be saved.
Your Action Plan
Hard Reset the Connection: Don’t just "fix" the connection. Go to Data > Connections, delete the Microsoft Bookings connection entirely, and create a brand-new one. This forces a fresh login and new tokens.
Check Conditional Access: Ask your IT Admin if there’s a policy requiring MFA or a "Compliant Device" for the Bookings app. If there is, the connector will fail every time because it can’t perform MFA for you in the background.
Escalate to Microsoft: If a fresh connection doesn't work, it’s a backend bug. Open a ticket and provide the Correlation ID, Timestamp, and Error Code. They are the only ones who can see why the "On-Behalf-Of" flow is failing on their end.
If a new connection doesn't fix the "Invalid Parameters" error immediately, stop troubleshooting, it’s a job for Microsoft Support or your Global Admin.
