Hi @Kevin_Rey
This part of the error message indicates that there is a problem with the input data to this step. Maybe check your data/settings again? Maybe the wrong column of data was selected for plotting. Or, there is an unexpected header?
You are also using a version of the tool that was sourced from the Test ToolShed, which means that it might not be “production-ready” or have unresolved development bugs. A better choice would be to install and use the versions of the tool suite from the Main ToolShed: https://toolshed.g2.bx.psu.edu/
Hope that helps!