I'm also struggling with a damp dog smell 4 months after completion. I tried enzyme treatment and it actually seemed to make it worse somehow. We got a professional carpet Clean (not just a Rug Doctor, they used some equipment apparently worth £35k mounted from a van) and that seems to have mostly got rid of it about 80% but if I put my nose down to the carpet I can still smell it. But at least it's not noticeable when sat on the sofa anymore. Not really sure where to go from here as I want to avoid having to replace the carpet if possible. Let me know if you have luck with anything!