UFH actuator/valve question

[Temp]

We have two UFH loops in our dining room and I noticed today only one was getting warm. Discovered the pin on the manifold valve stuck down which I know is a common problem. I removed the extension pin and its guide to get to the real pin and managed to free it up. Problem is the loop is still not getting hot. There are no flow gauges on this FAR manifold but I can feel the flow pipe to the loop isn't getting hot. 

 

So question is this.. If the pin is free to move does that mean the floor loop must be blocked or can it still be an issue with the valve? I have valves on order as they are quite cheap. 

 

The house is on three levels and this is one of two zones on the middle level not the lowest. System was dosed up with plenty of corrosion inhibitor so I'm hoping that's not the problem.