Hi Omar,
Usually with cockatiels, one bird sits during the day and the other sit at night. If the female is leaving the nest for long enough to allow the eggs to cool, then the eggs are not going to hatch. If this is the same pair you asked about, again I urge you to take the nest box away and rest them for a minimum of 6 months. The male needs to help, so if you try to breed them again in the future and he still fails to help, I would not breed the pair again. It’s too hard on your female to do all the work. As I mentioned, not all birds make good breeders or parents.
Thank you for asking Lafeber,
Brenda