Problem removing image files that did not load properly in Lightroom

I downloaded Lightroom at the weekend on Windows 11.  Yesterday I mistakenly tried to add too many images in the same batch.  It worked OK for the first 1000 images, but then for the remainder all had a triangle with an ! in the centre and did not add to the catalogue.  However, now if I try to add those images, either on the App or on the web version, it says they are already in the library, and does not add them.  On the web version it says they are duplicates and shows me the thumbnails with the warning triangle.  I have tried all of the ways I have seen to find those files and remove them, but I cannot find a way.  How do I resolve the problem? 

I am currently on the free 7 days, and want to resolve it before I decide whether to stick with it or not.   Thank you.