LR 12 Catalog will not open in Mac studio but does in LR 11.5. The catalog in question is on an external drive. I've tried to optimize the catalog and tried saving a backup catalog to the internal HD, which is grayed out if I try to reopen the backup in LR 12. The catalog in question is huge so it is not possible to export to my internal HD. A small LR catalog created on the Mac Studio in LR 11.5 DOES open in LR 12. Completely flabbergasted.