On Demand Workflow from Button

I am having trouble getting a button configured to run an on demand workflow.  I have followed the instructions from Scott Durow found here: https://ribbonworkbench.uservoice.com/knowledgebase/articles/132235-create-a-workflow-short-cut-ribbon-button-no-code.  Screenshots of the configuration are here:

Error when clicking button 1 or more records selected:

What am I missing?