Problem importing SilverFast Scans

It sounds like in your import process that you have selected Add, as opposed to Copy, or Copy as DNG. Ok.

If that is the case, then try this; select one image to import, change the method to Copy, the over in the Destination, change that from whatever is shown to a different folder, and import..

If that works, then go back and select another image to import, but change the method back to Add, and import.

If that works, then you are probably good to continue.

Possible issue is a previous destination got changes/renamed/moved/deleted, and LrC had an issue despite selecting Add. An occasionally, non documented, and lacking feedback messages.

Yes, this is about 99% unlikely, but easy to prove/disprove.

What is the name of those files? I have seen a few problems with people trying to import scans, because they named the files with a date, like "scan 01/05/2025" or something like that. In MacOS is it prefectly legitimate to use a forward slash in a file name, but not for Lightroom Classic. Lightroom Classic uses the forward slash as the separator in its file paths, so this date in the file name is seen as three folders/subfolders and so Lightroom Classic can't find the file anymore as soon as it starts to import it.

Would you mind sharing a couple  of these files (one tiff and one dng), so we could examine them?

You'll have to use Dropbox or some other file sharing service and post the link here.