Dragging images Lightroom

I found the culprit. My Bluetooth mouse is malfunctioning—nothing to do with Lightroom.

1. Restart your computer and try again.

2. Where are you trying to drop the images?  You can't drag photos to smart collections, for example.

3. Make sure you're dragging from the center of the actual thumbnail, not the grey border around the thumbnail. It's been a longtime misfeature that you can't drag from the grey border.

4. If those steps don't help, try resetting LR's preferences:
https://www.lightroomqueen.com/articles-page/how-do-i-reset-lightrooms-preferences/

LR sometimes soils its preferences file, and resetting it can fix all sorts of wonky behavior. That article explains how to restore the old preferences if resetting doesn't help.