I have a hayward h100idp1 that the fans turns on but never ignites, do not even hear any clicking sound or any type of an attempt to ignite

You have a ignitor problem .Replace the ignitor .Is it a direct spark or a glow type .My guess it's a glow type .About the fan issue sometimes fan would stay running for maybe a minute even after you turn the fan mode ofg

it is possible that all conditions are being met for the safety features: water pressure, gas pressure etc. there might be air in the line (instead of gas) get a licensed technician to bleed the line to the heater.
if you hear the clicking, the ignitor is firing. it might not be aligned properly for the burners to ignite. again, this is a job for licensed technician.

It sounds to me like you're looking in the right direction with the ignition module.I would replace it and then see what happens.Thank you

https://sites.google.com/site/haywardpoolheater/

Your propane supplier can help you with this.

Make sure the pipes are full of water. Check the thermostat to see if it is calling for heat. Make sure the thermostat is set to a temperature higher than the current temp of the water. If all those things are Ok then the unit may have gone off on high limit the last time you used it or the gas valve coils may have to be replaced. If there is a reset button for high limit press it. If not then the safety sensor for high limit may have to be replaced. If the unit fires up but does not stay on then the gas valve coils may need to be replaced.

make sure gas control valve is in the "on" position.the unit will cycle when in "off" position but you will never get main burner