ok then maybe it has pipped and filled the space with its body? I never candle during lockdown. I don't want you tossing the egg if it is good so leave it and hope for the best.
As to your question, no, high humidity is needed, it would not flood the air cell.
It's been one more day so has...
this egg is most likely about to explode.
Just make sure there really is no air cell. If the chick has pipped you would see that. If the contents have started to decay they will expell all air till the pressure is too big and bang.
Have you sniffed it? Have you tapped it? At day 21 I suppose...