WIRELESS MOUSE LOSES CONNECTIVITY FROM IMAC unless plugged in

Hello cch822,

Thank you for using Apple Support Communities! I understand from the information you provided that your wireless mouse disconnects from your iMac; I'd like to help.

The following support article provides some troubleshooting steps to try for this behavior:

If your Apple wireless mouse, keyboard, or trackpad isn't working with your Mac as expected - Apple Support

I hope this helps.

Best Regards.

Also if you have any USB 3.0 or TB 3 (USB-C) drives near your keyboard and mouse,

see > Resolve Wi-Fi and Bluetooth issues caused by wireless interference - Apple Support