IMAGES SAVED ON EXTERNAL HARD DRIVE DO NOT SHOW IN LIBRARY. Will show if I hit IMPORT so not lost.

Assuming you are talking about Lightroom Classic (are you?). Sometimes (maybe this is what you did), people do an Import but accidentally choose Copy when they thought they were going to Import using ADD. So in LrC, it knows only about the copies, which are in a different folder than your originals. 

You need to find these photos in Lightroom Classic. Please follow all four of these steps in the Lightroom Classic Library Module, in order.

1. In LrC, click on All Photographs (its on the left under Catalog)
2. In LrC, turn off all filters (Ctrl-L once or twice)
3. In LrC, Expand All Stacks (Photo->Stacking->Expand All Stacks)
4. In the LrC Filter Bar, search for one of these photos by File name.

PS: Please do not type in ALL CAPITAL letters.

You do not indicate whether you are using Windows or Mac. If using Windows, it is important to know that external hard drives may get assigned differing drive letters on different occasions (the next available letter, so something like E or F usually) - unless you’ve deliberately set a later drive letter (such as Z) for this device to always use.

Say that yesterday the drive appeared to the computer as E: drive, and you imported some photos from this using the Add to Catalog method. But today that same drive appears to the computer as F: drive. The Folders panel still remembers all these photos as imported on E drive but will show E drive as currently not connected. So all these photos will be considered in an offline state. You could re-browse everything to the F drive and everything would become normal again for now - but only until the drive letter next changed (for example, back to E).

So any external drive used on Windows should, I recommend, have a non-varying drive letter assigned.

If you are using Mac then drive letters do not apply: because the Catalog goes by the drive NAME. So your problem must lie elsewhere.

Here’s a good article about using Lightroom on multiple computers:

https://www.lightroomqueen.com/how-to-lightroom-catalog-multiple-computers/

Hi Suzanne,

The key thing to understand is that a photo only shows in the Library of the catalog it was imported into — catalogs on different computers don't update each other. Since everything looks fine on your other computer, first check that you are opening that same catalog here: go to File > Open Recent and compare the catalog name and path, and if the catalog itself is stored on the external drive, open its .lrcat file directly.

In that catalog, click All Photographs in the Catalog panel and set the Library Filter to None, then look for the new folder under the external drive in the Folders panel. That rules out a filter or a collapsed folder hiding the photos.

If the photos are selectable in the Import dialog, they are not in the catalog that is currently open. Please don't re-import them into a different catalog just yet, or you will end up with two catalogs and the work from the first one will not carry over. If this is definitely the right catalog, import them again with Add selected at the top of the Import dialog — that leaves the files exactly where they are on the external drive.

Background from Adobe on how catalogs work: https://helpx.adobe.com/ca/lightroom-classic/desktop/manage-catalogs-and-files/lightroom-catalog-basics.html

Hope that helps!