Some person "unknown"
pinched ours when "they" folded up the couch after use. If you don't fold the sides of the mattress to the center, it can be pinched when folding the back of the sofa up.
Look carefully for a small "pinch" hole on top by the sides .
Ours was in the "nappy" part.
I used a bicycle tire patch kit to make a repair.
Let most all the air out. You don't want to glue the top and bottom of the matteress together.
I scrubbed the area well beyond the large (about 1 inch) round patch and used plenty of cement.
Follow the directions on the card.
MAKE SURE THE GLUE IS DRY BUT DO NOT TOUCH IT WHERE THE PATCH GOES.
Peal off the bottom plastic and press on hard. Rub all air out.
Peal off top plastic and let the whole thing cure for 24 hours.
It should hold air just fine. Ours did and we are not lightweights.