You might have to get the mouse and the receiver (plugged in the USB Port) talking to each other.
I have a wireless KBD Track ball combo (ION) and about 3 times a year they stop talking.
Wireless devices can be multy channel and they must agree on what channel to use. In my case you cause them to resync like so.
Boath keyboard and receiver have a 'hidden button'. You press the button on the receiver and then push the button on the kbd.
LEDs flicker and they agree on how to talk to each other.
Of course that's what works here. You're milage may vary.
Check the information that came with the mouse.
If you lost the information googleing "Wireless Mobile Mouse 5000" should lead you to the owners manual.