Keyboard Not working Properly I have an old iMac on MacOS 10.13 High Sierra with the standard Magic Keyboard (before the current MK2). I normally use the iMac in Target Display mode, and then use Screen Sharing from my newer iMac to connect to it when I need to do something directly on the old machine. Naturally, I use the newer keyboard attached to my newer iMac.

A few days ago, I found that most of the keys on the old iMac appear not to be working. After a lot of testing, I can say the following:


The old keyboard connected to the newer iMac works well
An alternative Bluetooth keyboard connected to the old iMac also has the same problem
An alternative Wired keyboard connected to the old iMac also has the same problem
Everything is fine when I enter using the newer iMac keyboard on screen sharing
I have ensured that mouse keys and slow keys are turned off


All this suggest that there is a software problem.

I had it working for a while. I then restarted, and it worked for a while longer. Now it’s gone back to the problematic behaviour, and I can only type the a key, for some reason.

Any suggestions?
Thanks to your investigative work, it appears that the common problem is the Bluetooth on iMac.

Try resetting you BT.

You will loose paring so you have to pair it again.

To reset BT hold Shit+Option and click on the BT icon in the menu bar.

Now you will see the Debug menu.