Unable to Login Outlook iOS

Outlook for iOS is no longer allowing us to sign into our On-Prem Exchange 2016 servers. When trying to sign in on the new Outlook for iOS app updated 2 days ago we get the error “Unable to log in, please check you email address and password and try again”. I’ve triple checked email and username, and carefully put in my password multiple times. I can login to OWA and use native iPhone mail app with no issues using that password. This just started 2 days ago for a bunch of our Hosted Exchange customers. Anyone else experienced similar issues using the updated Outlook for iOS app and On-Prem Exchange?