Should it be easy to blow the coolant through the loop ?
My pump is running, but nothing get's pumped and if I blow I have quite a bit of resistant.
Res => Pump => GPU's in parallel => Mono Block => 480 XTX rad => 480 XTX rad => 240 XTX rad => Res
Pump is from this kit: Click
It worked before and the only differences are, that I have with this setup now a Mono-Block and replaced the parallel terminal with tubing.
That is a lot of components for a DCP pump. Chances are your issues are air bubble related.
That being said, double check your blocks don't have any blockages.