Please describe what you are attempting to connect using Bluetooth so we can give you more specific instructions. BT works perfectly in Monterey (we have 4 Macs with it installed) . If you are simply trying to connect a BT keyboard or mouse please follow the directions below:
The following will require any USB keyboard and mouse. If you don’t have them, borrow or buy them, they are inexpensive!
- Connect the USB keyboard and mouse to the computer.
- Open System Preferences – Bluetooth
- Un-pair the wireless keyboard and mouse.
- Turn off Bluetooth
- Restart the computer in Safe Mode per the directions in https://support.apple.com/en-us/HT201262
- Restart the computer normally.
- Open System Preferences – Bluetooth
- Turn on Bluetooth
- Re-Pair the wireless keyboard and mouse.
- Unplug the USB keyboard and mouse and begin testing the wireless devices again.