A couple of days ago the keyboards to two of my machines stopped connecting correctly via bluetooth. I swapped out the batteries but still now joy. I connected a wired keyboard and that works fine.

In more detail

When I switch the keyboard on it appears in the bluetooth preferences and displays a message asking for a passcode, however typing the numbers does not appear to register.

If I open up the bluetooth preferences I can see the keyboard and if I click the "connect" button again a dialog appears but will not respond to typing in the numbers.

I have a bluetooth trackpad which connects fine as do my AirPods. The fact that this has seemingly happened to two keyboards connected attached to two different machines is perplexing. Spent an hour with the Apple Genius Bar but no joy, they would not connect to the machine in the Apple Store which I guess means it is an issue with both keyboards.

Tried deleting the bluetooth preferences, restarting, taking out the batteries for a day…

Any other suggestions?