The low voltage alarm is indicating that there is a problem somewhere with your power supply. All that I can suggest is that you check each and every connection, check for corrosion, poor crimps on the terminals, it is still sounding like an intermittent connection or a high resistance due to corrosion of a contact.
You shouldn't hear any ignition clicking only the fuel pump after the glow pin has done its work.
I had a heater that I sold and the guy couldn't get it to work after he had someone install it - they had managed to insert a fuse incorrectly so that there was poor contact so do not rule anything out, check everything methodically, both power cables and negative undoing and inspecting every connection carefully. Change the fuses in case one is dodgy - it can happen.
You can try a start with a battery charger on the power source to raise the voltage up to 14v or so - if that works it is either a connection or the battery.