If your wireless mouse stops working, and you already changed the battery, you may need to reset the channel.
On the bottom of your mouse and the receiver you’ll find a little button. It may be small and require a paperclip to depress, or it may be a good size with the word “connect” near it.
Most of the time you depress the receiver button first, then the mouse. Check your owner’s manual to make sure (there may even be instructions on the bottom of your mouse).
Hopefully this solves the problem and you’re back in business.