Ok so I see you have Upgrade Modules are you holding Left Click or holding F (Make sure to hold F) also is it possible the items you tried to infuse are locked (The locks I am talking about are next to the name of the gun to the right side) That could be the issue your having or that its because you have that Item equipped (Hear me out I know you can infuse stuff while its equipped but there's a possibility that, that's the reason so just try it out) This probably won't help but its generally worth a try