When your window ac is not cooling it could be due to a clogged filter on the front of the Window AC.
Remove the filter on the window air conditioner and make sure it's clean and wash the filter out either with a hose outside or in your shower or kitchen sink.
Next clean the fins on the ac evaporator coil that is on the inside where you removed the filter.
When the evaporator fins on a window air conditioner get clogged with dirt or anything else then the window ac will not be able to work properly.
If you've cleaned the air conditioner and it's still not cooling your room down enough then you might need to get a larger window air conditioner or your window ac could be developing a slow refrigerant leak that is causing it to not cool properly and eventually once all the refrigerant leaks out it won't work.
If the window ac is just not cooling like it used too then it's most likely just dirty and needs cleaning.