I see now that you are posting in another's thread.
Get one or 3 of these:
https://www.amazon.com/Govee-Hygrometer-Thermometer-Temperature-Monitoring/dp/B09LTX95H3
There is no doubt your temp is off.
Your humidity may be way too high too,.
These work perfectly and you can see what your bator...
The humidity going down today is not what is causing this egg to not hatch.
The temperature has to have been too low for too long if they are still alive at day 21.
Let me go back and read from post one. BRB