Right, so you’re in an unsupported region for Gemini in regards to Brave. It always is helpful if you can try to search the forum a bit for answers. Not only would you have seen this as a discussion in the general FAQ that’s been flagged, but you’ll also have seen notices by Brave.
Anyway, Gemini has restricted which regions may link Brave to them for a while. ONLY people in the regions listed can link. You didn’t share which region you’re in, but for you to be receiving the Error you’re receiving, I’m assuming you’re NOT in one of the regions.