EK blocks are directional, are you sure you are using the inlet port? Also, I've not used a Distro plate before, but looking on EK's site, it looks like the ports are also directional (not necessarily need to go a certain way, but should be used for optimal flow). Could you possibly tell how your loop is configured? Comparing to the manual, it could be flow might not be going to the rad but that's from what I can see.