Today’s Question: After an update there are two folders that no longer appear in my Lightroom Classic catalog, though they are on the hard disk. I have not moved them. How do I get those two folders back into the catalog?
Tim’s Quick Answer: You can import the photos in folders that don’t appear in Lightroom Classic by either using the Add option to import those folders, which you can initiate by either using the Import command or the Synchronize Folder command for a parent folder.
More Detail: The first thing I would want to do in this situation is confirm that the photos that should be in the folders in question are indeed within the folders and do not appear anywhere else in the Lightroom Classic catalog, just to be sure. For example, you could browse the All Photographs collection in the Catalog section of the left panel in the Library module and then set a filter based on the capture date for one of the applicable photos.
Once you’re sure the photos aren’t in the Lightroom Classic catalog, you can import the missing folders using the Add option.
One way to initiate this process is to use the Import command by either clicking the Import button at the bottom of the left panel or by choosing File > Import Photos and Video from the menu.
If the parent folder that contains the folders you want to import is visible in the Folders list on the left panel, you can also initiate the import by right-clicking on that parent folder and choosing “Synchronize Folder” from the popup menu. Once the tally for how many new photos have been found appears, you can turn on the “Import new photos” checkbox, along with the “Show import dialog before importing” checkbox. Be sure that the “Remove missing photos from catalog” and “Scan for metadata updates” checkboxes are both turned off if they are available.
In the Import dialog select the folder (or multiple folders) you want to import, set the option at the top-center of the dialog to Add, and adjust any other settings on the right panel. You can then click the Import button at the bottom-right of the dialog to import the photos, which will cause the folders that were not present to appear again on the Folders list.

