Boiler not working after smart meter installed

Hi there, how do I get an engineer out as there appears to be no way to contact bulb outside of hours. A Siemens engineer fitted the bulb smart meter yesterday. I left the house straight after him and came home to no boiler (worchester) working, just a blue flashing light which apparently indicates low pressure. I tried to reset it with no luck. Also the gas option is not showing on the display . How do I get hold of bulb/Siemens to come sort this out?

I had a similar problem. Air in the gas pipe to the boiler.