Sounds like there is no/little circulation of water through the boiler.
If the water isn’t getting topped up, the boiler could overheat and trip a thermal overide. Go in the loft and check the header tank ball valve has not stuck and that the tank is full up to the ball. (assuming this is a vented system). If it’s a combi, make sure you have not lost water pressure – there will be no header tank. There’s usuually a water pressure meter inside combi boilers – consult your user manual.
Also check that the circulator pump is running. Put you hand on it to feel if it is turning.
The other thing to check is if the motorized valves are opening. I don’t expect this to be a problem because it is quite comon for the switch in the valves to “call” the boiler to start up.
Let us know if you find any of these affect the problem.