Hello cganti,
Thanks for reaching out through the Apple Support Communities about that difficulty with pairing your mouse with your Mac.
To verify, is your Mac currently running macOS 10.13 High Sierra?
If so, that behavior may be expected, as Logitech lists macOS 10.15 Catalina or later as a system requirement: Logitech MX Master 3 Wireless Mouse
Should you have any further concerns, you’ll want to reach out to Logitech: Logitech Support They’d be in the best position to verify the requirements for their device and troubleshoot any pairing issues further.
Take care.