Bluetooth problem in iMac (Retina 5K, 27-inch, 2020)

Try resetting the Bluetooth in System Preferences by turning it off and turning it back on again. If you have already tried this, try booting into safe mode and trying it by pressing the shift key on startup.

If that didn't work I would recommend reseting the PRAM and the NVRAM, to do this:

1. Shut down your Mac.
2. Press the power button.
3. Before the grey screen appears, press the Command, Option, P, and R keys at the same time.
4. Hold the keys until your computer restarts and you hear the startup sound a second time.

You may also want to reset the SMC, to do this:

1. Shut down your Mac.
2. Hold the power button down for 10 seconds.
3. Release the power button, wait a few seconds, then restart the computer.
4. If the problem hasn’t gone away, turn off your Mac again.
5. Unplug the power cord.
6. Wait 1 minute.
7. Reconnect the power cord and wait five seconds.
8. Turn on your Mac.

If none of these work please reply and we'll try to solve this problem.

If you're still out of luck, there is a console application that can display any hardware and system errors.

1. Open up Launchpad
2. Click on Utilities
3. Open the Console application.

This application gives an overview of your system.

To see if there is any problems, do the following:

1. Click on Start streaming.

Once you start streaming you should see a bunch of messages, but these are not what we are looking for.

2.Click on "Errors and Faults"

Now you should see all the errors of your system, go through them all.

If this doesn't help, on the sidebar are some options to look through

Hope I can help.