Please make sure ads are available in your region; I recently built a small tool to help with this: https://sampson.codes/brave/ads/my_region/. If nothing appears, ads are either not available in your region, or your machine is having problems communicating with the ads server.
If anybody is available for a screenshare, I’d be happy to accommodate your schedule to the best of my ability. Thank you, and I look forward to assisting with this issue further.