I do not know what exactly causes Firefox (on Windows 11 anyway) to block the copy and paste functions, but i found the easiest fix possible :-) Firstly, for me it never grayed out the copy option on right mouse click, so it seemed like copy is possible - just that it did not copy anything at all! The CTRL / C also did not copy anything - but in MS Edge everything worked just fine. I had cleared out the browser cache in FF - did not change anything (but maybe i should have closed FF and reopened it anew and things would have worked again - instead i got frustrated and used CCleaner to clean out the online trash in all browsers etc. But CCleaner also had a hickup due to some nag popup for their paid version, so i turned off the laptop and restarted it anew, then CCleaner ran normally, cleaned up all www garb. Now i opened FF - and guess what, copy and paste worked just fine again. Go figure what the cause was / is, but a www trash clean pc seems to solve it, that's at least something.