I recently tried to use the “Populate a Microsoft Word template” step in Microsoft Flow (currently in preview) to insert text into content controls, but ran into the error above.
The selected file doesn’t contain template elements.
The issue was that my content controls in the template were of rich text format and date. This preview step currently only supports plain text, combo box, and dropdown content controls.
So for all of your text fields, make sure you use the correct (plain text) control:
Once I replaced my rich text content controls with plain text, the content controls showed up in Flow as options for populating:
To keep this organized, I recommend giving each content control a title (in its properties) so you can easily identify each field when in Flow (select content control, then “Properties” from developer tab).