Aquasafe Question

[andsoitgoes]

Okay - so I just swapped out all my old, dirty prefilters for nice, new pretty ones.

Hooked it back up.

Put on the water..... and about 3 hours after that, it's not flowing. Should I have filled the pre filter areas with water, is there some magic trick I'm missing? Everything seems as though it's proper, it's no different than it was the other day - but I'm very confused. I know I lack in details what I don't make up for in pictures, but if anyone has any basics for me?

Tanks.