lockout

We recently moved into a new flat and had an absolute nightmare with the boiler. We have had a few problems fixed and today we have another. The boiler has locked out and when reseting it says there is 0bar but the gaugee by the filling loop says a good 1.5 bar. Any help would be greatful but starting to think might have to get the plumber on again who already has ideally it needs replacing

So angry as we live in only a 6 year old flat shared ownership and they wont give us any help