I have dogs. Cat urine carries a little more smell. I always have a bottle of PEE PEE, you can buy it at Petco. It neutralizes the odor so the cat will stop going in the same place. No odor, no mistakes. hopefully they will take it outside after a while.
Boy oh boy do I have some experience with this! I don't have a cat but I do have a VERY stubborn dachshund puppy who pretty much uses any carpet as his own personal bathroom. I tried steam cleaners, woolite, even home remedies that I got off the internet and honestly nothing worked. My neighbor, also a proud wiener dog owner, told me to try this stuff called Nature's Miracle. It smells like lemon and is supposed to remove the staind AND the smell. It also apparently is supposed to make them not want to got there again but I don't know about that one. You should be able to get it any pet store. Hope this helps!
To get rid of cat pee smell you can crush one cup, dried herbs like rosemary, lavender, etc. One teaspoon ground cloves, cinnamon and baking soda.Sprinkle the mixture on your carpet, let it sit for 10-20 minutes, then vacuum.
Moving forward after getting the smell out I would build a ventilated litter box (quite an easy DIY). It worked so well in our 1 bedroom apartment and now owning a house it's been even easier to implement. If you need a link to how I did our I can send one. Pretty much used a small motion sensor with a delay and 2 silent USB computer ventilation fans for the aeration. You can kind of see where the fan panel went in this photo. should've taken more "process" photos.
When I worked at a vet/kennel place, we had this stuff called Longone? Longon? Sorry, it been a while.lol. Anyhoo, I can vouch for this stuff. Its what we used there to clean bedding, towels, and aprons.