You could go to brave://rewards-internals and in general info tab check what region you selected. Do tell me your region.
Also, Gemini is now supported in the US only, so if you’re not from there. This issue will arise. This issue arises only when the brave rewards profile is a new one. Like, you installed brave newly on the device, reset brave rewards or reset the app or uninstall and install it.
This will not affect your already connected rewards profiles.
I seem to have selected Antarctica, which I don’t think is populated yet, at least not in a permanent fashion. I am not even sure how this happened. I selected US (where I live) for my two other linked accounts and those verified fine with Gemini.
I would hope I could prove, via the linked accounts (which share my bookmarks, etc. and which have been linked for months if not years) that I can verify my identity or county of residence in order to set the country correctly and verify with Gemini.
Well, Nope. You can’t do anything about being able to change the region to the appropriate one. You will have to reset Brave rewards and choose US.
Go to Brave settings → Brave rewards → Reset Brave rewards