Pipelines and Sharepoint - the Assigned To field

I have a pipeline working that creates and updates Sharepoint Items.  However, no matter what I try, I cannot get it to populate the Sharepoint "Assigned To" Field.

Even when I try to use Static Text, it does not update.

I have double-checked the Sharepoint API settings as best as I can and there seems to be nothing there prohibiting API updates.

I have tried various Jinja syntaxes and nothing takes.