After upgrading Lightroom Classic to latest version I cannot see or access my edited TIFF files?

These are old files that used to be in the catalog? If so almost certainly a filter that you don’t realize is there. Make sure you are looking at the folder and not a a collection. Check the bar above the grid area and make sure it says no filter or filters off at the top right. Quickest way to accomplish that is to click on none.

If you really have no filter active, try synchronizing the folder they should be in. Also check in file explorer if the tiff files are actually there.

Are you sure you don’t have an active filter, or are in a smart collection, that filters on raw files only?

Hi, ​@paulm6863178, quick question: Mac or PC?

Meanwhile, do you keep your TIF files in the same folder as the raw folders or are they on different folders?

Do you by any chance have a filter for raw files on?

Can you see ANY other types of files (JPG, PSD)?