Do you have a thermometer in the incubator, to know what the temperature is?
Most incubators switch the heat on for a while and off for a while, changing back and forth to keep the temperature right. So it might be working properly.
But things can go wrong with incubators, and the heat quits working. Yes, that would be bad for the eggs.
20 hours without heat might kill the eggs, but it might not. It depends on how cold the eggs actually got, and how long they were cold. That partly depends on the temperature of the room the incubator is in (if the room is hot, the incubator might stay warm enough for quite a long time; if the room is cold, the incubator will get cold much faster.)
Eggs are also a bit unpredictable. Sometimes they die really easily, and sometimes they survive things that seem really bad.
So I would check the temperature inside the incubator. If there is a problem, try to fix it. And after a few days, try candling the eggs to see whether they still seem to be growing or not. (Candling: take the egg into a dark room, and shine a bright light through it. Do an egg that has not been incubated first, then check the ones you are incubating. If they are growing properly, they should have dark areas of growing chick inside, that look obviously different than the one that was not incubated.)
