Several times, while working in PM+, I have wanted to look up something in my catalog and found that it could not find the catalog (although the catalog is on the file along with the other image and files on an external disk (same disk for everything!) It is clearly there, and may even have been updated recently, but not in the current session. Yes, I tried "locate existing catalog" in the "catalog management" menu in PM+!
Finally, I discovered that closing PM+ and then selecting the catalog on that external disk on my desktop, then dragging it to PM+ to open PM+, opened the catalog and it worked perfectly!
Something in the application is not talking to something else in the application and that needs to be fixed, I believe.