If you take the cartridge out, does the water flow properly?
I had trouble with my Penguin 150 once doing the same thing on a new cartridge. I finally took the cartridge out and let it soak in water for a day. Once I put it back in, it flowed properly. Never did figure out what it was...guessing maybe micro bubbles in the screen and carbon may have been restricting flow.
You may want to try the same thing.