Operations in progress stuck - after big tidy up

Hi all, first post and just learning about Lightroom. All has run well the whole time I've used it, but my first real problem came up and I don't know how to resolve it.

One day, I saw that all my photos had disappeared from Dropbox. Just gone. Couldn't recover them, no sign on the account anything had happened (that's a whole separate issue to sort out with Dropbox  In my decade of using it, never have I had a problem). I had a backup on an external drive but it wasn't up to date. When I copied all the files back and went to sort it all out, it looked like loads of files were missing, but of course they weren't, they were just in my 'uploads' folder instead of their final location. As I moved my files about, my ! icons decreased, which is brilliant.

However, after two days I still have '3 operations in progress' at the top of the screen with only the top bar showing any progress, and that's stopped. I did move a lot of files about but seriously, why would it just hang? What with this and Lightroom not being able to 'see' some of the photos on my hard drive to import them, I'm a bit fed up with how hard it seems to be to sort anything out.

Has anyone got any advice please? Do I just need to do a total fresh start on my catalog? Many thanks for your patience!