There are all sorts of interlocks on a modern boiler! Low water pressure, some have a sensor to determine there's a clog in the air intake, failure to sense the burner is on (flame sensor), and there may be more. If it was a transient fault and there's no reset button, sometimes just turning it off then back on will work. But, other than that, if it doesn't have any indicator lights or signals, you need to know and understand how to trouble-shoot the interlock system. Could be a bad relay, but it's probably an interlock from a fault. It could also just be a bad sensor (part of the interlock system). The manual often has some trouble-shooting. If you aren't comfortable, you may need to call a pro. Zapping a control board can get costly (if it has any!), and there's at least 120vac in there somewhere (and likely a bunch of 24vac for the interlocks).
The manual will have a theory of operation section that describes things that may help.