Cause
Various
Resolution
1) Make sure you have rebooted the computer and the mouse is snuggly connected to the computer.
2) If there are any batteries, try replacing them.
3) If there is software from the manufacturer that goes with your mouse, install it. If you already have, you may need to find an updated version of the software on the manufacturer's website and use it instead.
OUTCOME
Your mouse will resume operation.
Workaround
If the above steps do not work, try using a different mouse to see if the original mouse is no longer functional.