Magic Mouse 2 not visible

My Mac suddenly stopped pairing with my Magic Mouse 2. The charge level was not low, but I left it charging overnight anyway. There has been no change. My OS is up-to-date. I have followed the steps in all help files, but the step that says “your mouse is now paired” assumes correct operation. None of the documentation addresses what to do when it does not show up in the Bluetooth list.

The Apple support system will not let me get support on this device. It has a 17-character serial number (as indicated on the website), but the Apple Support app doesn’t accept that many characters and the website complains that it is an invalid serial number. I have checked and rechecked the number.

Help.