Using Outlook for Android in business environments for email and scheduling
The Problem was set to "resolved" by Microsoft, but now it is again under investigation: https://support.microsoft.com/en-us/office/outlook-and-other-apps-are-unable-to-connect-to-outlook-com-f4202ebf-89c6-4a8a-bec3-3d60cf7deaef
The "official" thread for this issue is also linked there, in which various information is collected/exchanged.