Here are your parts.

Double check to make sure the compressor is running. You can usually hear it and you should be able to feel it vibrating and it should be warm.

Is the compressor/condenser fan running.

Are the condenser coils and the front & rear vents clean.

If you took the back cover off reinstall it. It is required for proper air flow.

Is the evaporator/freezer fan running.

If the parts are clean and the compressor and fans are running, then remove the cover from inside the freezer so you can inspect the evaporator coils.

If they are heavily iced/frosted up you probably have a defrost problem.

If they is frost in only one area (usually where the freon enters the coils) or no frost then you have a sealed system problem. Be sure that this check is done after the compressor has run for a couple hours, if you do it shortly after a defrost cycle you will come up with the wrong conclusion.

A sealed system problem will be an expensive repair as you need a pro.
It could be a freon leak, a clogged sealed system or a bad compressor.
Often it makes more sense to put those dollars towards a new unit.