How do we get the LPG central heating boiler working again ?

Hi, our lpg tank ran empty so the central heating boiler stopped working

We have now had the tank re-filled but the boiler won't start and displays EA and RESET

We have pressed re-set many times but the boiler just runs for a minute or so and goes back to re-set

Presuming there is air in the lpg supply pipe is this a job only for a gas fitter ?