Cooling unit is SEALED and under high pressure (300# Plus)
NO..altitude does not affect fridge as in 'low ammonia' etc.
Low ammonia means LEAK and then there is NO ammonia/hydrogen gas etc
Altitude does have affect on fridge cooling......thinner air----fuel rich...cooler flame for heating
What's a person to do?
Well there isn't a 'high altitude kit', there isn't an 'air shutter' to adjust air ....fridge has fixed air inlet based on propane gas flow/pressure.
Need to check that burner flame is strong,steady, blue.
If yellowish/lazy then need to get more air to burner.
Remove lower vent cover and see if flame improves.