I had this problem recently, it might be your issue.
I have many security certificates installed by various programs in my Windows 10 Personal Store. When 0AD tries to connect, it uses wrong info from the first 'valid' certificate it finds, whereas having none at all connects fine. Reinstalling Windows, Creating a new Windows user or removing the certificates in the Windows 10 Personal Store does the same thing to fix that issue. To check, just hit Win+R and type certmgr.msc and look at the Personal/Certificates folder. If you have certs in there, it may be the issue. I was able to back them up and remove them to test it out. How to back up security certificates
May be an issue with how mTLS interacts with Windows
