You either manually moved or renamed a file in the ArchiCAD folder hiearchy. (You must NEVER do this even if you want a library to be somewhere else - just leave it.)
Or... your permissions have gotten corrupted inside the folder on your Mac. Rare. You can check just to be sure:
Force Time Machine to do a backup.
Launch Disk Utility, select the drive that your AC folder is on (probably main HD that contains Applications folder).
Select the First Aid tab, and click the button "Repair Disk Permissions".
Cheers,
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB