DO NOT BYPASS THE PRESSURE SWITCH.
With the burn box full of gas, you will blow yourself up and burn down your home.
You mentioned that nothing is happening on a call for heat.
This may be due to a bad venter motor. Check for power at the venter motor during startup to see if the venter motor is bad. If this the first startup of the season, you may have to bump it a little with whatever you can get to reach the windings or fan blades. Nurse it with a little white oil and you should be fine.
The pressure switch is not being made, due to the venter motor not coming on but, once the venter motor satisfies the pressure switch, the system will go into ignition mode.
Check for any resets on the transformer, overloads (if applicable), roll out switches, etc....