Hi there! It looks like this post on Reddit may be able to help you:
https://www.reddit.com/r/Surface/comments/dxyybk/surface_pro_7_brightness_issues/f7yra6q/
"
- install Intel Graphics Command Center from the microsoft store
- go to system tab (it's the tab on the left hand side with 4 boxes)
- select power from the tabs on the top
- turn off display power saving
"
Hi
I have The same problem with my surface pro 7. I installed and applied these changes but didn't work for me. :(