Oct 26 2018
The latest update, or recent updates, we have experience users losing their Exchange account access.
Current version is 2.100.0
The only remedy is to uninstall the App from the iOS device, reinstall, and re-configure their accounts.
I have also experienced this with newly configured devices that have not had exchange accounts fully configured, but the app update had been applied.
We user an MDM to distribute apps and updates.