Vokera Mynute 14SE not heating immersion?

The pilot light for my boiler(above) went out last week. I managed to get it back on but since then the immersion(boiler) will not come back on. When I turn on the heat, it will heat the radiators but not the main boiler. I didnt change any other switches, just reset it last week. Any ideas on how to fix this or do I need to get a plumber out?

Cheers