Hey. This error is caused when you try verifying in a region which isn’t supported for verification as of now. Brave has limited verification to 20 countries as of now, but they’re planning to get workable countries running by the end of this year. They’re working on getting Brazil right now and next is India.
Also the website you provided is showing you countries which are supported to view ads for brave rewards and that has nothing to do with verification. You can still participate in Brave Rewards and keep earning BATs and claim them each month. They’ll be stored on local files so do make sure you don’t reset or reinstall Brave so as to Keep your BATs on your device.
The link below will show you countries supported for Brave rewards verification →
Also the information about how Brave is working to get countries back for verification is on the page given below →