Perform these checks before calling an engineer, they could save you money:

Is the gas supply turned on?
Make sure all your heating controls are on and calling for heat.
Do you have a room thermostat? If so, ensure it's set at a high enough temperature.
Check is the power supply switched on
Check the fuse, if it needs to be changed ensure it's the correct type (3-amps)
Do you have the gas boiler set on timer? If so, check that the clock is set at the right time.
Do you have a channel programmer? Check to make sure that it is actually in 'heating mode'

If you are still having problems

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