Photo Search

Where is the library located? If on an external drive how is the drive formatted and connected to your Mac?

Try rebuilding the Spotlight index for the volume that the library is on via this Apple document: How to rebuild the Spotlight index on your Mac - Apple Support  

You are searching for a category, like "beach." Have you tried searching for keywords? Same results?

When things don't make sense, the usual steps to try are

• Restart the computer (of course)
• Use another library if you have one, or make a small test Library with a few pictures in it and see if the same thing happens.
• Make a new user and see if the same problem recurs with it
• Start in Safe Mode (different for different computers) This bypasses certain potentially disruptive processes.

           Start up your Mac in safe mode - Apple Support 

• Try rebuilding your Photos Library by closing Photos and re-launching by option-command-clicking the app icon.

One of these steps may fix the problem, but their failure to work is also diagnostic.

Let us know what happens.

If you just recently installed a system upgrade, you may have to wait, until Photos has scanned your Photos Library again for the categories. Keep your Mac connected to a power source and running over night to finish the scan. Right after the macOS 14.1 update my Mac had also problems to show any categories and found only photos with the text "beach" or "bear", but a week later it got better.

Is Spotlight working elsewhere on your Mac?

Have you installed and run any "cleaning", "optimizing", "speed-up", anti-virus or VPN apps on your Mac?

How are you searching? Spotlight? Finder? Search inside Photos? Are you searching for keywords? or categories, like "fireworks?" Tell us what you're doing and how. You're using the Mojave OS?