well I had the same issue with these fittings.
what happens is if it is NOT perfectly square (as close to 90 degrees to the base of the fitting), it will spin but not engage the threads...
I'll use this post to update MY EK parts
2 x Titan XP - Nickel water blocks
2 x Titan XP - Nickel back plates
1 x Supremacy EVO Elite - 2011-v3
1 x EK-FC Triple Parallel - Plexi