DearD Parisien,
Welcome to Microsoft Community.
I understand that the issue you are currently experiencing is that the Surface Pro 6 keyboard is not pairing with the Surface pro 6.
For Microsoft keyboard issues, we have a special support article that provides the appropriate troubleshooting steps. If you have not tried this before, we recommend that you try step by step first and see if the issue is resolved.
Troubleshoot problems with your Microsoft mouse or keyboard - Microsoft Support
If you have tried this before and the keyboard works fine on other devices, then there may be an issue with your Surface device itself, which will need to be sent back to Microsoft and checked, and you can refer to the following link for the steps to do this:
How to get service or repair for Surface - Microsoft Support
I hope this information helps. If you have any updates, feel free to let me know—I’ll be here to help.
Best regards,
Tamara-Hu | Microsoft Community Support Specialist