After I upgraded to 12.04 LTS my middle mouse button stopped working... it worked fine before the upgrade. I can scroll with the wheel but when i push it down it refuses to work. Can someone tell me how to make my mouse work again?
The same issue persists with Ubuntu 17.10 and Xubuntu 17.
I found this helpful, too:
These instructions guide you through customizing your mouse, including reconfiguring the middle mouse button: https://help.ubuntu.com/community/MouseCustomizations