Then you are not in a supported country, at least not to link to Uphold. You can check https://support.brave.com/hc/en-us/articles/6539887971469-List-of-supported-regions-Custodial-payout-accounts to see which ones are supported and Pakistan is not listed.
It doesn’t matter whether Uphold allows you to create an account. What matters is whether they are permitting Rewards integration. They frequently add and remove the capabilities in various countries for a number of reasons.
It sounds like your only option at this point would be to try to get an on-chain invite and receive payments directly to your Wallet. If this interests you, then you should check out PSA: Current and upcoming changes to Rewards and Creators - #8 by Saoiray