When Auto Zone checks the pressure and finds it low, I would certainly believe there is a leak in the system if you lost charge after 2.5 years of it being charged. Auto Zone will have a self contained charging can with a charging gage attached to recharge your system. However, you may want Auto Zone to add a can of leak detector dye to the system before the system is fully charged. The leak detector will, over time, color the fitting that is leaking. Instead of the leak detector dye, you could elect to have the system leak detected by external means to get the problem solved now rather than wait for the discolored fitting. I'm not sure Auto Zone will have the leak detector equipment but I'd think they could send you to some place that could like Goodyear or Firestone. I suspect you'll find one of the connections to your condenser the culprit.
Whatever route you chose to find the leak, that self contained charging can should charge your system to fully operational.
I suppose it could be a fuse, but these are easily checked. Ask Auto Zone to check that out for you Or you could do it yourself. Your fuse panel will be housed under your dash and will look like a small board with fuses. that panel may have a cover on it. Feel around that panel for a latch. That latch will release the panel to swing down such that the fuses can be seen. You may have to remove a cover from the fuse panel. The panel will identify fuses and you will be able to remove the one for the air conditioner and visually check it.