I'm always amazed at the throw everything at it approach to cleaning upholstery. In this video called How to Remove Cat Urine From Upholstery they use as many cleaners as possible to remove the cat urine problem without really any thought to how the ingredients react to with one another. It just seems like they are emptying their pantry onto the sofa and hopes the smell goes away. I have been cleaning upholstery in Tampa FL for years and I can tell you these home brewed cocktails of cat urine cleaner don't work.
If you have a cat that has urinated on the your sofa then the best thing you can do is use regular tap water to rinse it out. If your cat has peed on a sofa cushion that can be removed I recommend using a clean white towel to soak up all the excess urine. This is a good time to check to see if any color has transferred from the upholstery to the towel. If you see any color coming off the upholstered item onto the cloth then you should stop cleaning and call professional upholstery cleaner.
If it's color safe then I recommend going to the next step. Take the cover off the cushion and rinse the urine out under a faucet. Use room temperature water and use a lot of it. I recommend rinsing the cushion padding out with a hose or in the bathtub. Squeeze it thoroughly as you rinse to help massage the urine out. Next hang the cushion cover out to dry and place the cushion padding in front of a fan to speed dry it. Once everything is dried out you can reassemble the cushion and get on with life.