Either there's no moisture in the house (especially if you have an air conditioner), the coils are not cold enough, or there's no air flow across the coils. if the latter is the case, clean off the rear coils, clean off the front filter (or if no filter, the fins), and see if the fan is working. cleaning the condenser coil fins in the front would also help with it not getting cold, if that were the problem.
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Either there's no moisture in the house (especially if you have an air conditioner), the coils are not cold enough, or there's no air flow across the coils. if the latter is the case, clean off the rear coils, clean off the front filter (or if no filter, the fins), and see if the fan is working. cleaning the condenser coil fins in the front would also help with it not getting cold, if that were the problem.