That's the worst for camping. Been there. Try inflating it and spraying some soapy water all over; bubbles will show you the spot. Tiny holes are sneaky. Once you find it, dry it off and slap on a patch with good glue, you know, the kind that sticks to vinyl. Let it cure for a day. Works great. Or if it's too much hassle, just return it to Amazon, their policy is pretty solid. Don't suffer through flat nights. Yeah, fixed mine that way and it's held up for months now.
