When you cleaned the furniture, did you use an enzyme cleaner? You have to get rid of every single, solitary bit of pee/poop smell, or else the cat will continue to "go" in those same areas.

 

Don't use the scat mats. Sorry, but aside from them being a huge pain in the bum (possibly in a literal sense since they'll be going on the sofa...) they could actually make the issue worse depending on the cause, AND they're awful.

Ok, this is what I have done to re-train cats to use the litter box:

-Confine the girl to a bathroom with everything she needs in there. Plan to have her completely restricted to the bathroom for a month - DON'T skimp on this! Breaking the habit is the most important part and a week won't cut it!
-At the same time you need to have that couch cleaned again, ideally right at the beginning so it has a whole month to air out before you begin letting the kitty out again.
-If she uses the box that entire time then you can begin letting her out when you are able to supervise. (This is the part where most people rush and end up where they started.) DON'T give her free access to the house in the beginning! Watch her closely and if she goes to the couch don't take your eyes off her! If she squats as though she's going to pee calmly pick her up and place her in the litter box. Do this for another month.
-If there are still no mistakes you can begin letting her out most of the time and see how it goes. Hopefully this process will have worked and she'll have been trained back to the litter box.

I'll add one more note...I'm really sorry I have to say this, but you need to be aware of the possibility that it isn't just her that's been peeing on the couch. Usually in a multi-cat home once one of them starts they'll all start doing it. Luckily, once you get the cat who started the problem to stop the others will usually stop as well, since they're just going where it smells like the litter box rather than having some reason to avoid the box.

Just in case you don't have this covered, here are some basics you didn't specifically mention in your post:
-You have the right number of boxes, but if they're all side-by-side in one room it doesn't count. They need to be scattered around the house. The reason for this is that some cats can feel trapped in the litter box, and other cats may wait outside to pounce them. This is a main cause of litter box avoidance. (Heck, if someone tackled me whenever I left the bathroom I'd avoid it too!)
-Try different litters. In one of the four boxes try a completely different kind of litter, to see if she's more attracted to it. I'd also give Dr. Eleslys (sp?) cat attract litter a shot. It definitely helps.
-Have some boxes that are covered, and others that aren't. Some cats prefer to be hidden when they go, others need to see what's going on around them.
-Feliway plug-in. It's definitely worth a try. Many members have had a lot of success with it, and I noticed a pretty big difference in my home as well.
-Stray cats. Often cats (including my boys *sigh*) will spray if there are strays spraying outside your house. If there are strays you can use deterrent sprays, or motion detecting sprinklers, to discourage them from coming around.
-Scoop the boxes every day. When the strays start coming around it helps SO MUCH to have clean boxes. If I forget and dont' scoop one day both boys are pretty much guaranteed to spray if they see one of the strays. If the boxes are clean they run over and use it instead. HUGE difference.

 

I had it cleaned by ChemDry and they said it was enzyme solution. This is my second sofa and love seat because of this.

 

A month to confine her sounds good. I have placed her in my sunroom overnight before and I have to say the little cries to get out melt my heart. The videos did not show other cats, but once I saw it was her two times in a row, I turned it off. Cameras will go back up just to be sure.
Their litter boxes are in a storage room that is accessible through a cat door from my laundry room. It would be hard for another cat to sneak up on them, but you never know.

I've just bought Natures Miracle Just for Cats Urine Destroyer, natures miracle oxy formula orange citrus, and dumb cat ant-marking & cat spray remover. I am willing to try anything to make this behavior stop.

 

if the litter boxes are all in one place one of the cats can easily guard the entrance to that room from the others. Cat guarding isn't obvious, and most people (myself included, until I started paying close attention) don't notice it's even happening. That's why it's SO important to have the boxes in different locations - so they can't guard them all!

 

When you went to the vet, did they check for a UTI? Cats that pee somewhere besides the litter box often indicates them having a UTI. I am thinking that she could have a UTI, because she is peeing on the couch. Or was there a death in the household, did a cat or dog or person she bonded to, pass away? Cats do get depressed when losing another pet or human and they may use other places to go to the bathroom.

Cats can be really stubborn, you have to be more stubborn than them. A month to confine her probably will work to get her to use the litter box again.

 

She was checked for UTI and it was negative. That was my first response that she's was sick, but not the case. We haven't lost any pets. She could be jealous, but who knows. She is not super affectionate. She likes to be near you but not on you when it suits her to be. And she seems to be a offer person cat and that is with me.

 

Sorry spell correct... She seems to be a one person cat and that person is me.
I do have a dog, but that is not a new thing for her.

 

You did a great thing by taking your fur child to the vet right off the bat to have her checked out. I would suggest two things...first of all....get a blacklight and have your entire place checked out. Make sure that this is not the only place there is urine. Second...and maybe more important than the first....get a second opinion. I'm am sure that you vet is well qualified but everyone can make a mistake. If it were my "child" I would have it done. Good luck to you

 

I would try taking the cushion covers off the seats and putting the foam cushions in the bathtub and soak with enzyme cleaner. Buy a couple gallons. Soak, squish it through and through with your feet, soak some more, squish some more then rinse, rinse, rinse and air dry in the sun. ChemDry gets the cushions and maybe top 1" of foam clean, but the funk goes deeper than that and it is still attractive to the cat. I agree that putting them in a room with no fabric furniture or carpeting will help recondition them to using the box.