If you are using a Magic Mouse on a PC, scrolling won't work without specific drivers. New Magic Mouse USB-C Does Not Scroll - Apple Community
Here is a step-by-step guide to getting your Magic Mouse scrolling again. magic mouse not scrolling
Sometimes the configuration files that store your mouse settings become corrupted. If you are using a Magic Mouse on
: Turn the mouse off using the switch on the bottom, wait a few seconds, and turn it back on. wait a few seconds
A recent macOS update can sometimes reset your preferences, or the mouse may be in a state where it is recognized only as a generic pointing device.