Alt and Shift keys not working

Hello there,

Can anyone tell me please whether this is a settings issue or some kind of glitsch? I am experiencing 2 issues:

1. In Illustrator, the Alt key + click  and drag usually duplicates an item. I've been using this shorcut for years but for some reason it is no longer producing a duplicate function. 

The function works perfectly well in Photoshop but illusrator just stopped being responsive to this shortcut. The funny thing is, occassionally it does work - just randomly, now and then even when I've done nothing different.

2. The shift key when held down and selecting various objects, usually allows me to select multiple objects. In the swatches panel, all of a sudden, I've noticed it randomly allows and disallows the use of the shift key like this.

This is a brand new computer (PC) running Windows 11.

Does anyone have any ideas what might be going on please?