liebherr gn2556 upright freezer

HELP We've just aquired the above freezer. You turn it on the light works, there is noise at the back but it doesnt get cold. The LED just flashes two dashes. We have tried going through the different codes. It is not in demo mode. We cannot see any F codes but what does come up is the following: E3 15,E8 0, E4 14. Please can anyone throw any light on this?. The previous owner thought it needed regassing but I keep reading that its usually the sensors that go. Dont want it regassed only to find that there is still another fault. I had been stored in a garage for a short while but I dont think this is the problem. Appreciate any ideas. thanks

if the compressor is running but not getting cold it can only be one of two things, a gas problem or compressor valves may be faulty. need to get it checked by a fridgie.