Start Workflow / Start Data not recognized

Version: 2.3.13.0

I'm trying to call a workflow that has a required choice field with 2 possible text strings, but the string is not recognized by the starting workflow, I get  "Failed to start workflow. Value does not fall within the expected range." in the WorkFlow history. I've confirmed text string accuracy, Any ideas on how to troubleshoot ?

Here is a snippet from the Start Workflow, Configure Action pane 

Thanks,

Heshy