
Are they vinyl tiles or ceramic? If they are vinyl the problem may be that they have been had their polish regularly removed with ammonia. A wash over with a solution of biological washing powder should remove any deposits, which of course has the same scent as urine, and help discourage further peeing. Rinse it well off after letting it remain for about 20 mins. If they are ceramic goodness knows why any smell should be lingering

but you could treat it the same.