Graco Pack‘n Play Owner's Manual page 6

SNAP!
4. When setting up, lock rails
BEFORE lowering center.
Be sure top rails have become
rigid. If not, pull up again until
they are rigid. If top rails do not
latch, lift the center of the floor
higher.
CHECK that fabric covers
corners.
5. Hold one end of the unit up and
push the center of the floor down
until locked securely into place.
6. Always use mattress/pad soft
side up.