The blank Rewards screen is a known issue. Posted the link to the Brave GitHub issue report below. Appears the fix will be released in the next version update.
Rewards page blank with devtools errors
As for not being able to reconnect with Uphold, that is probably due to the current payout issues that Brave dev is actively working on at the moment. However, you may want to try the steps below, this was a workaround that was successful for many users in the past. May still work for you. You didn’t say if you were receiving a message when you tried to reconnect. Most users were receiving a “Something Went Wrong” type message in this scenario.