I’m not exactly sure why, but I noticed the storage was full and no one had deleted my Immich. I found the files in Root/var/lib/casaos/files/appdata/big-bear-immich, so I moved the folder to DATA/AppData/big-bear-immich. After that, everything worked perfectly. I have no idea how the files ended up there, but everything is running smoothly now.
Thank you very much.