I'm currently on DL419 JFK-LAX. I applied a RUC and I'm the 1 and only person on the upgrade list. After the gate closed, the app showed 5 available DeltaOne seats. I asked the purser to upgrade me, and she said she's not allowed to, only the gate can, and she has no way to communicate with them (though we haven't taken off yet). So I'm flying this in C+. Was the purser correct that she couldn't upgrade me?