Authenticator and required Android settings for compatability

Question

Recently updated Galaxy S9 from to Android 10 / OneUI 2.5 from Droid 9 / OneUI 1.0

After successfully registering a corporate O365 email account in Authenticator on the phone, that account cannot successfully be added to the phone e-mail app (9Folders). When attempting to add the account and submitting a valid password, Authenticator issues and APPROVES the sign-on request acknowledging the random 2-digit code for 2FA, but immediately following the APPROVED response, the app gets stuck in a "loop" for approx 10-15 secs (looks like the full-screen frame jumping up and down from the top) then bounces back to "Pick an account" where the process started. BTW all three other email accounts were added back to the 9Folders app without issue (though none required used of Authenticator) Logs sent to 9Folders app developers reveal failed attempts when attempting to add the corporate account, but no errors within the app itself.

This same corporate account was added to and worked perfectly with Authenticator and the mail app on the subject phone with Android 9.

Any help would be appreciated.