I had this exact issue, and tried everything suggested in this community including a complete wipe and re-install on my Suface Pro 6. Days of effort to no avail
Question for you - before this issue occurred, did you ever run a third party driver utility like Driver Booster or even the Intel Support Assistant? Several others reported they did this and the issue started after doing so. Did you use the downloadable recovery image to wipe and reinstall your SP6 and did you have this issue after using the recovery image or did you perform updates and then experience the issue?