Lightroom Classic folder shows "No Photos in Folder" although the photos are in the catalog

If Lightroom Classic shows ‘No photos in folder’ while it does show the photos in ‘All Photographs’, then this is often caused by a corrupt ‘Catalogname Helper.lrdata’. Move that out of your catalog folder (Lightroom will rebuild it) to see if that solves the problem.

Thanks to your answer, I think I found an important detail that may clarify the problem.

Show in Explorer opens:

D:\Google Drive\Google Photos\2010\09

and the photo is physically located there.

However, Lightroom's Folders panel does not show a folder 2010 under D:\Google Drive\Google Photos.

Instead, Lightroom shows a completely different folder:

D:\2010\09

That folder is the one that reports 1 photo, but when I select it Lightroom displays "No Photos in Folder".

The same photo can still be found under All Photographs, can be edited normally, and Show in Explorer always opens

D:\Google Drive\Google Photos\2010\09.

So it looks as if the photo belongs to the Google Drive folder, but the Folders panel shows a different folder tree (D:\2010\09) that reports the photo count but does not actually display the photo.

Does this suggest that the folder hierarchy in the catalog has become inconsistent?

Thanks for your immediate reply, very much appreciated..

I already tested exactly that.

• Show in Explorer opens the correct local folder (D:\Google Drive\Google Photos\...).
• The photo is found under All Photographs and can be edited normally in the Develop module.
• If I try to import the same file again from that exact folder, Lightroom says "This photo has already been imported."

So Lightroom definitely knows the correct file and its location.

The strange part is that selecting that same folder in the Folders panel still shows "No Photos in Folder."

In addition, Go to Folder in Library does not work correctly, and Synchronize Folder produces the internal error:

UNIQUE constraint failed: AgLibraryFolder.rootFolder, AgLibraryFolder.pathFromRoot

That's why I don't think this is simply a case of importing with Copy instead of Add.

Symptoms

• The photos definitely exist in the catalog.
• I can find them under All Photographs.
• I can edit them normally.
• Show in Explorer opens the correct local folder.
• If I try to import the same file again, Lightroom correctly reports:
  "This photo has already been imported."

However, when I select that folder in the Folders panel:

• Lightroom displays "No Photos in Folder".
• The folder badge still shows the correct number of photos.
• The status bar at the bottom says 0 photos.

If the photos are found under All Photographs, then you need to right-click on one of these photos and select Show in Explorer or Go to Folder in Library. This will tell you what folder the photos are in. Obviously, the photos are not in the folder you think they are in; you are looking in the wrong folder in the LrC folder panel.

Why does this happen? Because you probably accidentally imported using Copy instead of Add. So the photos are now in a different folder than you think they are in. LrC knows only about the  copy it made, and doesn’t know about the original in the original folder that you think the photos are in. LrC thinks they are in a different folder and so you have to look in that different folder.