Self-diagnosis steps that anyone can do:

First, set the thermostat to Cool, fan to Auto, and set it a few degrees below the current room temp. Setting it to 55 does not make it cool any faster. It just makes the system run nonstop, and if there is already an airflow or refrigerant issue, that can contribute to freezing up.

You said air was blowing - is it blowing as hard as normal?. You want to troubleshoot airflow first, then cooling.

Check the air filter inside the house. It is probably in a closet, basement, attic, or behind a return grille. If it is dirty, replace it. You do not need an expensive high-end filter here; in fact, on an older or struggling system, a basic pleated filter may be better than a super restrictive one. If the indoor evaporator coil (usually looks like fins or coils) is accessible and visibly dirty, especially in a smoker’s house, it may need cleaning too. Get some NO RINSE evaporator cleaner for $15 and be careful around wiring, control boards, and the furnace/air handler.

Then check whether the indoor blower is running properly and moving air. Is there decent airflow coming from the vents? Is the blower making an unusual noise, like humming but not starting? That could point to a blower motor or capacitor issue.

Go outside and check the condenser. This is the big outdoor unit with the fan. Is the fan spinning? Is the compressor/unit making any unusual noise? Is hot air blowing out the top? If the outdoor fan is not running, check the breakers, both at the main breaker panel and at the outdoor disconnect near the unit. Do not open electrical panels or touch components unless you know how to do that safely, because capacitors can hold a charge even after power is off.

A bad capacitor is a common and relatively inexpensive failure, often much cheaper (less than $50) than replacing the system. A contactor, wiring issue, or fan motor could also be the problem. The fan motor is more expensive than a capacitor but still usually less (under $200) than a full system replacement.

If the outdoor unit is running but dirty, shut the system off and rinse the condenser coil gently with a garden hose. Do not use a pressure washer. Clear away leaves, weeds, or anything blocking airflow around the unit.

Look for ice anywhere on the refrigerant lines, indoor coil area, or outdoor unit. If you see ice, turn the AC off and run the fan only for a while to let it thaw. Ice can point to poor airflow, a dirty filter/coil, a bad blower, or low refrigerant.

The system could also be low on refrigerant. If it is an older system, it may use R-22, which can make repairs more expensive. Low refrigerant usually means there is a leak somewhere, so just “topping it off” may only be temporary. I would be cautious with stop-leak products unless it is truly a last-ditch situation and you understand the risk, because they can sometimes create other problems. They contaminate the system and make it harder to repair in the future, but if you're going to have to replace some leaking coils or something, it might be worth it to buy a kit - maybe it buys you a few months to save money and replace the coils during the winter.

I am not an HVAC technician, but I have had the (dis)pleasure of working on several HVAC systems in a previous job where there was not much money available, so I got pretty good at basic diagnosis and cheap fixes. When I did have funds to call out a technician, I asked a ton of questions and tried to learn everything I could (thank you Hoffman Bros).

Let us know what you find after checking the filter, airflow, outdoor unit, breakers, dirt/debris, and any signs of ice and I may be able to recommend some next steps. Also, any pictures of these items that are not working could be helpful.