Can only have been left too wet or you've brought some old soiling or an old spillage back to life.
Either way it looks like a recall, a pain for sure but this time have a good look around for signs of an old spillage. Lift the carpet if possible as it could even be a problem with the underlay.
Cleaning again I'd turn the pressure down a bit, use less water accross the main area but really flush through any specific problem areas. I'd use a deodoriser both in the pre-spray and in the tank.
How can you not know what chem you used?