Suggestions:
*Try connecting an external USB keyboard to your Surface Pro 8.
**You may try Onscreen Keyboard.
***If you have a Recovery Drive, boot from that by pressing the Power button while holding the Volume Down button. Once in the recovery environment, you may be able to use the keyboard to access troubleshooting options.
**** Perform a Hard Reset. Press and hold the Power button and the Volume Up button simultaneously for about 15 seconds.