This error we faced as well since last week and resolved this by fully removing and re setting up our outlook channels. However, in return we are now faced with an authentication error that disconnects our outlook channels every 60-90 minutes. "Remote API returned authentication error: (invalid_request) AADSTS900144: The request body must contain the following parameter: 'refresh_token'. ". I logged a support case since almost a week with QB but unfortunately no resolution. Also just posted a discussion on that in this forum to see if others have found resolutions to that.