Problems with Photo search function

Thanks for your suggestion, but Spotlight isn't the issue. There is no problem with Spotlight searches.

My problem is limited to search function in the Photo application, one that has always worked seamlessly in the past. Photos which are named have always been retrievable by this means, but now a "name" typed into the search field immediately gives a "no results".

I have also tried to retrieve photos by their image number to no avail.

I can search for an album name, but that is no help when I need a specific photo.

Again note that I am running Mojave OS 10.14

Thank you, I will try that. Just did a back-up to an external drive as I have seen posts of significant problems after rebuilding the library. But these were in early days (2018) and hopefully those problems have been dealt with.

Unfortunately rebuilding my photo library did not correct the problem; searches for photos by name are still unsuccessful. Incidentally, I notice that the titles of many of the photos are ghosted out, and it appears that due to some previous program iteration, the names assigned are (in some cases) now considered file-names, not titles. This may be unrelated to the problem however as filenames also fail to appear in searches.