This is just a simple set of steps to follow, it’s by no definition of the word extensive. This only applies to Windows, I may update this for certain linux distributions in the future.
1. Confirm that the mouse is securely connected by disconnecting then reconnecting it.
2. Try connecting to a different usb port; also try using a different mouse that is known to work.
3. Confirm that any lights on the mouse are lit when it’s connected to the pc.
4. If wireless, confirm that the mouse is switched to on with working batteries and paired to the pc.
5. If the keyboard is still functioning, use it to uninstall then reinstall the mouse drivers:
5A. Bring up the Run box by pressing the Windows Key + R then run devmgmt.msc.
5B. Press the tab key until the name of the pc is highlighted, then use the arrow keys to highlight Human Interface devices.
5C. Expand it with a right arrow, press enter on the mouse’s entry, use a combination of the tab and arrow keys to access the Driver tab.
5D. Use tab to highlight the Uninstall button then press Enter. Go through any prompts uninstall.
5E. Close the Properties window with Esc then highlight the pc’s name at the top of the list.
5F. Press Alt then use the arrow keys to access the Action menu then select Scan for hardware changes.
5G. Windows should then recognize the mouse hardware and reinstall the driver for it.
6. Reboot the pc into safe mode with networking and run a malware scan.
6A. Tap the F8 key once or twice a second immediately after pressing the power button on your computer to turn it on. Keep Tapping F8 until you reach the Advanced Boot Options menu.
6B. Use the arrows on your keyboard to select “Safe Mode with Networking” then press Enter. If asked to choose the OS, just press enter again.
7. Run your anti-virus/anti-malware software, let it update to the latest virus/malware definitions is possible.
If all else fails, ask someone else for help!