Direct answer
Document in the Airbnb app first: time it stopped, photos, and whether neighbors/building staff see the same issue. Ask for an ETA and backup (shower access, partial refund, or move) — escalate to Airbnb support if the host goes quiet.
Message the host or co-host through the platform first, note timing + photos if visible leaks, and escalate per Airbnb support if response stalls — parallel-call building admin if it looks building-wide.
