If the stain is not lifting after multiple treatments, I would buy a new bottle of hydrogen peroxide. Peroxide loses its potency over time, especially if exposed to sunlight or the lid is left open too long, etc. Make sure your baking soda isn't too old, too. You could also be trying to treat a stain that isn't urine. I cannot guarantee this solution works on all mattress stains (like oil and dirt and sweat) though some have said it worked on other stains on the mattress as well.