Have HVAC Questions? Ask an HVAC Expert for Answers
So far it sounds like there is an outdoor temperature sensor in the system, and that the programming might be set up to keep the boiler off until its below 65F or so outside.
Please attach a well focused, close up photo of the wiring diagram glued inside the service panel,you can use the paper clip icon at the right end of the toolbar at the top of this dialog box.
If there is no paper clip icon, look for the '+attach files' link at left of your send button.
I can mark it up with trouble shooting instructions.
You will need a multi meter ($30 at a hardware store) and some experience working with appliances, let me know a lot about your skill sets in those regards.