Magic Mouse Right Click & Scroll Aren't Working

Try cleaning the laser surface. I am guessing you are using Magic Mouse one. Turn off the mouse and with a Q Tip moistened, not wet, with white spirit, swizzle the Q Tip around on the surface of the laser itself. It may have got soiled during use.

If you are using a USB mouse with a scroll wheel, follow the same path but apply the Q Tip to the wheel, then turn the mouse upside down and vigorously rub the mouse wheel in circles on some clean white cardboard for 20 seconds of so. You should see black marks and possibly some fluff and dust appear.

Let me know your progress.

As it is out of warranty there is little else you can do except remove it and reconnect to your machine as if it were a new mouse and reset all settings. They are not repairable.

The replacement would have to be a Magic Mouse 2, suitable for all MacOS's from El Capitan and upwards. Magic mouse 1 is no longer stocked, though you could pick one up in Amazon. I think I would favour the new version.