Your boiler is currently on standby because your thermostat is set too low or the boiler is switched to summer mode, meaning it is waiting for a request for heat.

DIY fix possible

Check if the boiler is set to 'Summer' mode (hot water only) and switch it to 'Winter' mode if you need heating.Turn up your room thermostat or programmer to ensure it is calling for heat.Check if the batteries in your wireless room thermostat have run out and replace them if necessary.