Advice for spraying

Does anyone have any advice for spraying ? I have a cat that has been checked out by the vet many times but they don’t know why she sprays. I actually just got new carpet and she already is peeing in a new area on the stairs. I’ve tried to use the diffuser plugins but it didn’t seem to help. Is there anything I can do? Today she did it again and the boxes were just cleaned. She also likes to claw at the new carpet which is very frustrating.