Edited to say I'm very sorry you lost your babies, but don't give up.
It is ok to open the incubator during lockdown as long as you make sure the humidity stays up. Even if you don't know if your temperature was right, I would always candle the eggs if they go part day 21. If you see that they are still moving at that time, you should make a hole in the top of the air cell, especially if they have internally pipped. If they have not done anything else after 24 hours, I would try to help them hatch, as long as you have good instructions to follow. If you leave them in there for too long they will die. If you help, they may still die, but they may survive.
I'm going to get people saying never to do what I say, but I have not lost any of the chicks that I have helped. Especially with shipped eggs, because of the shipping, a lot of times they end up malpositioned and they can't hatch on their own.