Check if there is any unusual obstruction to the air flow through the evaporation coil (inside) - a seriously dirty air filter or a bad air handler motor. Can you feel the air coming out of the registers with normal force?
If the air is moving OK, the sealed part of the AC system may be low on refrigerant. Since you just put it in, I wonder if they charged it properly or if there's a small leak in the system. If there's a leak, the problem will become worse until it just stops cooling altogether.
Verify the air movement first. There may be other issues with the system, too, but they all require dealing with the sealed system and the refrigerant. Since an EPA Section 608 card is required to work with refrigerant, it is out of reach for a DIY repair - need to call a pro.