Apple released an update to macOS Monterey on the 13th December 2020, taking it to version 12.1 for all users. Unfortunately, however, the update which provides SharePlay, Apple Music Voice Plan, Hide My Email, and other features aren’t showing up for everyone.
We’ve experienced the issue ourselves on an M1 MacMini and, after some digging around, have found a quick and simple fix that should work for all users.
Open a Terminal window (Utilities –> Terminal.app) and issue the following command.
Sudo SoftwareUpdate --fetch-full-installer --full-installer-version 12.1 -R
The command will ask for your password (you need to be an Administrator), and once the download is complete, the installation wizard will start automatically.