This used to happen to me last year, but hasn't happened in a long time. I just had a race where I was CC to fuel certain amount and it was recognising the command, but the '#21 litres' message that appears in-sim when that command is successfully processed wasn't appearing. Then I pitted and the fuelling command in black box was set to 0, so I had to do another stop a lap later and set the black box by hand before stopping.

Has this been a known issue recently?