Mouse doesn't work

Mouse was working okay a while ago but I disconnected it to use it on another computer. It did connect to the other computer after a 5-minute wait, but now won't connect to my original computer, a Mac-mini.

I had the same problem a week ago and brought it to our local store where a "genius" fiddled with it and finally zapped the P-ram. That worked until now.

Fortunately I have a $20 mouse meant for a PC, so I can still use my computer but it's very frustrating to pay for something that simply does not work.