Portable Indoor Airconditioner not cooling -- let's discuss possible reasons (and solutions)
If it's not an obvious mechanical failure, it could be (a) a problem with the controls or (b) a refrigerant leak.

Symptoms of control problems would be the compressor not turning on or not staying on. You should be able to hear it turn on/off distinct from the fan; if you aren't hearing that, then it may be repairable by replacement of a thermostat or the unit's control board.

A refrigerant leak would be likely if the compressor and fans are running fine, but it's not cooling. One sign of this would be constant running of the compressor. In a partial leak, you may find that a section of the coil is freezing over. Maybe you saw that last year?

If it's a refrigerant problem, the system could potentially be recharged. This is not a DIY job as the refrigerant chemicals are environmentally and personally dangerous, and require special equipment to recharge. You could try calling some appliance repair shops to see if they would do this repair.