my boiler wont ignite had it pressure tested it passed that so was told it cant be gas .code e1.33 keeps flashing it goes throw cycle but wont ignite had one of the spark type plugs out tested it it sparked .so now we are stuck /
you'll need to have you're co2 ratio's re-set. job for a qualified engineer with a performance tester / telegan. if unable to re-set ratio's then new gas valve required. relatively common problem, which is less likely to occur if it's being serviced properly.