Sup /sci/,

I need to remove a stinking piss stain from a couch. Topside there's no damage to the fabric, but the piss dripped down to the underside and that's where the stink is the strongest.
I used some carpet/furniture shampoo but that didn't help much.
Copious amounts of baking soda helped with the smell but it's still lingering a bit.

Any ideas what else I can try on the sofa to get rid of the stench?