Recently I came across the following error in panels where I am using Sankey diagram: Failed to load source for Sankey Diagram visualization
I have installed Sankey Diagram - Custom Visualization App version 1.0.0 on Splunk enterprise version 6.4.3.
(Same issue persists for upper version of app)
Based on the comments mentioned at link, I have tried deleting my browser cache and checked app version compatibility, but no luck.
It works perfectly fine in Chrome but not in IE (version 11.0).
Since Sankey Diagram Custom Visualization is supported by Splunk can you open a case with Splunk?