Since you've already shown that the mouse USB doesn't work with either a mouse or the keyboard, try getting a new mouse. Or at least, get a new cable for the USB. A better option;, many mice and keyboards come as a set and work with a single wireless USB plug in the back of the computer. Both devices use the same wireless USB plug. Give it a try.

Next, if you haven't already, be sure to replace the batteries in both the mouse and keyboard.

Hope this helps