Open the zipped egg up. If it's been that long it's most likely weak and exausted. Possibly dead. To help it, very gently take off the place it has already unzipped, be careful of rupturing a blood vessel. If the chick is gonna survive, it needs to get out of the egg now.71% and it’s been steady above 65% since lockdown - and mostly above 70%
Can you still hear it chirping?