Here is an excellent website for problem solving with hatching. I hope it helps and you have a more successful hatch this time around.
http://edis.ifas.ufl.edu/aa204
There could be several factors here. One being you may have had a temp spike (beyond 103) that lasted for some amount of time and it wasn't caught. Were the eggs turned in the last three days of lockdown? Lockdown meaning you stop turning eggs and increase the humidity for the last three...