New Post: Help with SEC Graph Metrics

I am a communications scholar trying to use SNA (first time!) in my research.
I am using "Tweeting Apart: Applying Newtwork Analysis to Detect Selective Exposure Clusters in Twitter" to guide my work.
I managed to get up to "selective exposure cluster method" (p.204). After completing the required steps my "overall metrics" graphs read, "not available", save the "in-degree" graph.
Did I miss a step or maybe doing something wrong?

Please advise. Kind thanks.
C