Pet stains can be a problem especially on wool carpet . They can be insoluble to cleaning products after the initial soil removal . The nature of the stain can cause a chemical 'burn' & a dye stain, especially if old. Removal would be difficult without pro equipment- Its not just a spray on and watch it disappear. I,ve found remove what you can with your prefered product and flush with machine, treat with microbiolical digester ,rinse, treat any remaining stain when dry with reducing agent(browning treatment)
Mike