Hey OP, this isnt really the right instance for tech support, i suggest you post here: https://lemmy.world/c/techsupport
That being said, it seems most likely to me that step 5 indeed caused your issue, judging by the fact that Windows is complaining about file permissions, which you changed. Have you checked exactly which file you changed the permissions on?
If you can find that file i recommend simply undoing the changes in step 5.
Just repeat the steps from step 5 up to 5.4, where you should see a little box that says change permissions next to disable inheritance. You should then see a button to enable inheritance. enable it.
Then, change back the owner to Administrator and readd any removed users from the permissions section.
click apply, reboot your pc, and the problem should be fixed.