@AlanFord running as administrator is generally not a good thing to do. There have been some known issues that arise from it due to changes in Chromium and also how Windows occasionally handles things. I know Mattches is trying to run you through some other things and may be able to get you to a solution.
That said, I’m wondering if your issue might be as was discussed in the topic at Brave doesn't start when I run it as administrator and Brave Shield doesn't work - #41 by clifton, with me linking specifically to one of the guides on how to resolve it.
Also make sure you right click on the icon for Brave → Properties → Compatibility → make sure you have Run this program as an administrator unselected. If that’s selected then it may cause issues. Many were saying Brave won’t launch if that’s selected and disabling it resolves it all.