Illustrator not copying. This is extremely serious issue.

What exactly are you trying to copy (Text, c=vector objects styles)? Please provide an example and what version OS & AI are you running?

Am not aware of any global copying issue. We can probably help you if you can elaborate. 

If you want help, you might start with telling us your system and Illustrator version. Exactly what are you copying exactly where and in which way does it not work?

Are you working remotely on the computer?

Please explain more clearly just what the problem is. To say that "Illustrator is not copying" doesn't mean anything. What is it not copying? Illustrator is, after all, a drawing program. It is not meant to copy anything (with the exception of Image Trace which recreates in vector raster images). Are you referring to copying and pasting? Please state the problem clearly so that help can be offered.