American Fridge Freezer switches on but doesn't cool

[Gav74]

I have an "old" American style fridge freezer, RSH1NHMH.

It was working fine, then stopped. Everything defrosted, fridge got warm.

It still switches on OK, display works, makes quiet noises (fan I think). It lets me set the temperatures and displays the current temperature, but it never gets cold.

It's out of warranty and I could do without having to pay for an engineer, so any ideas on what I might need to fix or replace would be greatly appreciated. 

[Gav74]

Picture of fridge freezer

[Pugs1957]

I wouldn't mind betting it has to be regassed so it may have a leak somewhere.

[Gav74]

Is there any way to check?

[Pugs1957]

It probably needs special tools to diagnose and then there's the refrigerant which I think you need a license for.
I like a challenge but this is one even I would swerve.

[AndrewL]

@Gav74: What temperature do you currently have the fridge set to, and have you tried lowering it? Can you check to see if it says 'Vacation' in the top right of your display? If it does, press the Vacation Button to disable this feature. 

Can you also check if the fridge is  in direct sunlight, or near a heat source? Is the back of the device too close to the wall, and preventing air from circulating? 

[Gav74]

It's set to 3 degrees, I've tried lowering it, nothing happens. Current temperature inside is around 10 degrees.
Definitely not in vacation mode, I checked that.
It was in direct sunlight for a while, and probably too close to the wall too. I've moved it since, but it still won't cool/freeze.