The Rapoo 7800P appears to be a very cheap device since it's found on the Chinese websites, therefore the issues you're having. In most of the cases, you won't need a driver to correctly pair the device with your PC. Uninstall it and let Windows handle the driver. Also, if it's a wireless one, simply attach the dongle to PC and then turn on the mouse.
If that doesn't work, then the mouse is faulty and needs replacing. Contact the seller and explain the situation, because it might be possible to obtain a refund as well.