That would most likely be because your region is not supported at this time. You can read details at PSA: Unsupported Region
You can still go to Uphold and login there, but you can’t link Brave to it. So your balance can be checked on Uphold’s website. But you can’t link Brave to it, which means payments can’t be sent to Uphold until they add your region again. Until then, you’ll be claiming BAT to your browser only.