Mp3tag 1.13.1 on macOS Sequoia 15.7.4 shows “Please move Mp3tag to your Applications folder” even though it is installed at /Applications/Mp3tag.app.
mdfind "kMDItemFSName == 'Mp3tag.app'" returns only /Applications/Mp3tag.app.
spctl --assess -vv /Applications/Mp3tag.app returns accepted, source=Notarized Developer ID, origin Florian Heidenreich.
codesign -dv /Applications/Mp3tag.app shows valid TeamIdentifier SX5YR25689.
Reinstalling from a freshly unzipped download gives the same result.
See here?