Hi Inloopwinkel
I do not think it is possible to change the PIN on that keyboard, and so, if you can connect another keyboard successfully, there may be a problem with your keyboard, try taking the batteries out of the keyboard, then wait a while, re-insert the batteries and then try pairing the keyboard again.
Yep, I have done that: batteries out -> wait -> batteries back in
but It makes no difference whatever. I still haven't got a clue what the PIN for my keyboard is and I can find no documentation that tells me. Therefore I assume 0000 may be just a rumour - where is that documented? Note from my new question: https://answers.microsoft.com/en-us/windows/forum/all/can-anyone-help-resolve-a-problem-with-the-pairing/dbc5f0d8-86da-4f46-942a-69cbb58cac5c) that my latest investigation shows that my Windows 10 PCs never asked for this PIN and the problem I'm having with my "troublesome" Microsoft Bluetooth keyboard appears to be caused by Windows 11 which seems to have added the need for this undocumented PIN by telling me:
"Enter the PIN for Microsoft Bluetooth Mobile Keyboard 6000"
Why can Windows 11 not go back to the way Windows 10 worked for adding a Bluetooth keyboard and stop asking for the PIN?