On my TS-364 I also got the “not logged in” error. I removed the Roon Server. I removed the entire Roon directory. Then I installed Roon again in a directory called M_media and I started the Roon Server again. After selecting to open the Roon Server config screen I got the same error again.
Then I degraded the firmware to TS-X64_20230603-5.1.0.2418 and again the same thing happened. Next step was to degraded the firmware to TS-X64_20230421-5.0.1.2376. Started Roon Server en selected the config screen and it worked.
My only conclusion can be that the from 5.1.x.xxxx on Roon Server does not work on either of my Qnap devices the TS-453A and the TS0364. And I don’t like it!