PC Algorithm Causal Inference What are some reasons why the PC algorithm might generate zero edges for a certain dataset? How and why could this happen?

The PC algorithm starts with a complete graph (all nodes have edges to all remaining nodes). In the first step all node pairs are tested for conditional independence with conditional independence tests, suspect to a certain threshold. If those tests suggest conditional independence between pairs of nodes the edges are deleted from the complete graph. As far as I am concerned all remaining steps are concerned with directing the edges between nodes.
Therefore, the only (theoretical) solution to your question is that all your variables in the dataset are conditionally independent with respect to the threshold of your CI-test (reasonable/default values of that threshold should lie between 0 and 0.05).
