All my images and PDFs have disappeared

My Roon core is on OpenSUSE LEAP 15.3. Things were working, but today, the new albums I put on the core disk had no cover art and the PDF links did not work.
I assumed this was due to file permissions. The new albums had different owners. The owners were all subsonic:squeezeboxserver, but I removed subsonic from my system, so changed it all to jar:squeezeboxserver
Now I see no cover art at all!
Every file on my Music directory has read world access, so I do not understand this. The music files (in same directory as the pdf and cover art) play perfectly.
Do I have to rescan somehow when ownership/permissions change?