"Bluetooth preferences will not load: Since I updated my OS to Monterey my MacBook Bluetooth won't work, which means Airdrop and Phone synching don't work either. Even though I appear to be able to turn on Bluetooth, it doesn't do anything. Bluetooth preferences cannot be accessed from the menu bar or the App bar."
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Single Out this User:
For temporary use and troubleshooting purposes, create a new Administrator User, log into it, seeing if all shows up as it should. If so, then it is likely an issue with the current user itself. If not, then it is an issue with the MacOS, and you need to reinstall the macOS. Once determined, delete this Administrator User you just created.
Reinstall the macOS:
Nothing would be lost. It's just that misplaced items would be placed back to where they should be and corrupt system files would be replaced by clean files. Go Here: Reinstall macOS - Apple Support. Use the third bulleted method: [command + r].
Important: Prior to installing an update or performing a reinstallation, to prevent data loss, be sure to Back up your Mac with Time Machine. Ding so, you will have something to restore your Mac from, should anything go wrong after the reinstall.