This is issue has been going on for awhile with worsening symptons. We opened up this ticket awhile back when it was just the web interface that wouldn't work and after upgrading to 2021.1, we can't connect to the managed domain at all anymore. Ticket Link
I have contacted Microsoft Support to make sure that the domain is working as intended. When we view the wireshark files, we see the connection come through as successful but Adaxes says the password is incorrect. We have created a new service account, and tried several account options without success. We have a firewall in between our adaxes servers and this secondary domain but our security team has verified no blocks and has down a tcp dump to ensure nothing else is going on such as an application firewall or any other type of drops. Something in the authentication seems to have changed with this version.
I would like to schedule a call with your team, us, and microsoft support to get to the bottom of this. Having a separate install is not a viable option.