mitsubishi fdc200vs no heat

His guys.dont know whether you can help.i was called out to a fdc200vs multi split which the customer says there's no heat.started it up on heat and the compressor runs for 30 seconds and shuts off.if I switch it to cooling the pressure in the suction line pulls straight down to 4 bar and shuts down.if I switch the mains off you can hear what sounds like a valve opening and gas feeding.when it stops the controller shows the sun and a hand and shortly after the controller shuts off and the red light flashes. anyone have any ideas.thanks

have you checked the gas charge? 410 system should be 8 bar, interogate hp ,lp alarms have to alarm a few times to generate a fault code- check the remote controller for operation data, will tell ya sensor values and comp current, comp freq
if its a cassette sometimes have issues with hi condensate float switch sticking, also filter door switchs fail too

hi
what about on cooling mod ? same problem u having ?