Take it one step at a time. First, does the pump turn on? If yes, do you have it connected properly? (i.e. IN and OUT lines correct and not reversed) If they are correct, disconnect the OUT line and activate pump. Does water pump? If yes, look at the OUT line valve. Is it turned ON. Usually though, the valve is there to turn off the water while you change the pump. I'm guessing you may have the in and out reversed. Confirm that please. Is there a in-line strainer that needs cleaning? Finally, what else did you touch while changing out the pump? Thanks Dennis