Good work on the install!
Repairs of the electronics related items on board, can be a lot more complex however.
Lets do this test:
The boiler may be failing somewhere in the ignition sequence, this test will tell me where it is failing, and I will know from that what component we need to test.
Stand next to the furnace after the thermostat has been turned off for 5 minutes. Listen intently as someone else turns the thermostat to heat and sets it for 85F.
You should hear the small inducer fan start right away.. then a faint click after 1 to 3 seconds, that is the pressure switch closing.
....then in 15to 45 seconds you should hear 2 more faint clicks, that is the ignition relay and gas valve relay closing.
....then within 5seconds you should hear the main burner fire..
In about 30seconds the main blower should come on.
If the main burner goes off after 2 to 5 seconds or within a minute or so tell me about it and the number of seconds involved.
Repeat that a few times until you get familiar with the sounds, then tell me in detail how far the sequence goes before it stops.
Tell me please if this is identical to the wiring diagram glued to the inside service panel of your unit or not.
If it is, I can mark it up with trouble shooting instructions.