Same problem - no solution yet. I'd prefer to add the Pinterest widget from the Pinterest developer tool site but the code they gave me didn't work.
Pinterest says Don't forget to include pinit.js once per page, right before the closing </BODY> tag. but I didn't know how to do that. I've seen tutorials that don't mention that bit so I assumed it wasn't necessary. Given the fact that I couldn't get the widget to work, I'm now thinking it's something important! Any advice about how to add this second bit of code would be much appreciated. I'd like to put the widget in the footer.