Hi Chad. Typically a refrigerant leak is the culprit, especially in older units from consumable parts such as O-rings. If due to a refrigerant leak the low pressure safety switch will prevent the compressor from starting to prevent seizure, the fan will not normally turn on unless the compressor does as they are usually on the same circuit. Take it to any refrigeration repair shop listed under HVAC in the yellow pages. They will pull a vacum on the unit and check the leak down rate, chances are it has a leak and the refrigerant leaked out.
They will then locate the leak , repair it and purge the unit with nitrogen. After purging it will be evacuated again and then recharged and op checked.
I have a degree in HVAC and repair chillers part time.