Looking at
https://community.brave.com/latest
Sounds like your trouble is the Agony of the Day: August 1, 2021 - among several Brave Rewards followers.
Answers might be found in:
Funding Your Brave Wallet:
“https://brave.com/funding-your-brave-wallet/”
Brave Rewards:
“https://support.brave.com/hc/en-us/categories/360001053052-Rewards”
Brave Rewards FAQ:
“https://support.brave.com/hc/en-us/articles/360027276731-Brave-Rewards-FAQ”
Update: New and improved “Estimated pending rewards” (Brave Ads earnings) counter coming in v1.27
Monday, July 19, 2021
“Update: New and improved “Estimated pending rewards” (Brave Ads earnings) counter coming in v1.27”