I have a Gear Head 2.4Ghz wireless mouse. The left-click button doesn't work but the right-click does. When I move the mouse over the pad, I can see the arrow moving on my screen, but when I try to left-click on anything, nothing happens. I had sent out my laptop to repair the monitor, and prior to sending it out, the mouse worked fine
Computers & Internet - Gear Head - Mouse
Answers & Comments
It's more than a coincidence that the mouse malfunction started after you got your PC back from repair. I suspect the settings have changed.
Go to your menu and scroll down to settings, then to devices and select "Mouse". It will walk you through the settings and you can make the necessary changes. Hope this helps!