I have this same problem. I followed the instructions from Desktop support:
1.) Before clicking on the solve option, open brave://rewards/. Then slightly move the captcha to click on the BAT Purple triangle besides the URL bar (if you are able to click on the BAT triangle, then no need of moving the pop-up, just click on solve). Click on the solve button. A captcha will appear immediately below the BAT triangle (from the triangle), where you need to move a circle in its position.
2.) A screen recorded video of solving it will be posted shortly.
3.) Link this post as s…
From: For the users who are not able to solve the Ad Captcha
This does not work.
Where is the video (#2)?