Sorry to hear you’re having issues with accessing your Qobuz account within Roon.
It’s worth noting that your primary server machine - the Rhein Z1 is an unsupported device. It would be worth temporarily setting up Roon Server on your Windows 11 and test to see if the same issues occur in this temporary setup.
I recently replaced my Rhein Z1 Plus with a Rockna Wavelight Server. The Rhein had been working perfectly for weeks, but as soon as I tried to log in on the Wavelight Server, this problem started again. If it doesn’t get fixed, it’s fine — I’ll just use Audirvana instead of Roon, since that one never has these issues.