It's the urine. Try sun bleaching it by spreading out the piles to get rid of the ammonia.

Ammonia is produced when there is excess nitrogen. More carbon is needed if there is ammonia. You want to capture as much of the nitrogen as possible. Sun bleaching just bakes the ammonia off and kills the microbiota of the compost.

Compost troubleshooting guide: - smells like sewer = not enough oxygen - smells like ammonia = not enough carbon - smells sweet/fungal = just right

Underline that. As I learnt it, compost mostly benefits from drying, baking it in the sun.