1. Make sure all connections of the kit and breastpump are secure.
2. If single pumping, make sure the port plug is placed into one of the single pumping ports.
3. Make sure white membrane is laying flat against the yellow valve head.  Check that the yellow valve head is clean and not damaged.  Refer to the assembly instructions.
4. Make sure the diaphragm cap or faceplate on the front of the breastpump fits evenly and securely.
5. Make sure the ends of the tubings are fit securely into the backs of the breastshields and into the ports on the diaphragm cap or faceplate.

Which size personalFit breast-shields comes with this breast pump?

This breast pump comes with 2-24mm & 2-27mm breast shields.

Is the pump built into the bag or can it be used separately without carrying the bag?

The breast pump is fastened to the inside of the bag with Velcro strips so it can be removed if needed, however i found the bag very handy though,

the flap in the front unzips and folds down it kind of acts as a tray to hold everything and protects the furniture, surfaces etc.