Smog test

having problem with vehicle passing smog test 3rd time now had the cat replaced need feedback please!!

Telling us what the vehicle make, model, year, and engine type are would be very helpful.

You posted this on the old board with zero info. You have now posted on the new board, also with zero info.

State you’re in, mileage, year, make, model of car, mileage, any Check Engine Light on, exactly how did they fail you, what readings were you given, any maintenance done in recent memory, etc.
Leather seats? What color paint? Anything at all might help.

Just changing the spark plugs and air filter helps many cars run their cleanest. Once at the test station, DON’T turn off the engine. The engine has to stay at full, uninterrupted, operating temperature. Also, while waiting to be tested, you could keep it in DRIVE, with hand brake and foot brake set, and idle speed increased a little to keep the engine hot. If the check engine light is on, they won’t do the test. Then, take the car an auto parts store for a free reading (scan) of the check engine light. Bring any trouble codes here for comments and advice.