Using Outlook for Android in business environments for email and scheduling
I had somthing similiar. The early hours of Tuesday 29 October my Outlook app on Andriod stoped working. Windows app and web mail were fine. Got authentication error went attempting to connect. Tried uninstalling the app, Authenticator, restarting the phone with no joy. I also have my own domain hosted by Go Daddy. The solution that eventually worked was....
Uninstall or clear data in the Outlook app
Add an account
Untick the suggestions and click continue
Enter a dummy address for your domain e.g. imloosing ******@mydomain.com
Choose work account
This will take you to the Go Daddy sign in page
Replace the pre filled imloosing ******@mydomain.com with your actual 'prefix'@mydomain.com
Boom! (Hopefully)