Make sure all connections of the kit and breast pump are secure.
If single pumping, make sure the port plug is placed into one of the single pumping ports.
Make sure white membrane is lying flat against the yellow valve head. Check that the yellow valve head is clean and not damaged. Refer to the assembly instructions.
Make sure the diaphragm cap or faceplate on the front of the breast pump fits evenly and securely.
Make sure the ends of the tubing’s are fit securely into the backs of the breast shields and into the ports on the diaphragm cap or faceplate.