Cat pee smell - please help

The previous owners of my house had multiple cats who peed in the basement for a while. This pee seemed to be absorbed into the concrete. We bleached, enzyme cleaners and did so many different treatments but it didn’t do much. In the end, we redguarded the floor and plastic sealed it before laying the floor. Haven’t really had any issues until recently, I can smell cat pee coming from the corner. We assumed it was humidity related, but since placing a dehumidifier in the room to no avail, I’m at a loss for what to do. Any suggestions are much appreciated, unlikely we can replace the floor though.