Here’s what consumers have asked with answers from ParkSleepFly staff and previous consumers.
Clearly a scam, they only reply via email and have an impossible refund policy - ou canceling their reservation directly with the hotels, which hotels cannot do. Then providing PSF with their cancellation number before they'll honor a refund.
The parking isn't actually free in my experience. You can get a lower hotel rate without the parking. When you ask for the rate with parking the price goes up, often comparable to booking the hotel separately and paying separately at airport park n fly spots. But the convenience is worth something.