"You are not authorized to perform the requested operation" when configuring piston

I’m finally taking the plunge and have installed CoRE with the intention of moving my stuff from Rule Engine. I’ve followed the instructions here to install CoRE: http://thingsthataresmart.wiki/index.php?title=CoRE#GitHub_Installation (including turning on OAuth for the app)

But… Whenever I click “New Piston”, “If…” and then “Add a condition” i get the red “You are not authorized to perform the requested operation” error. I’ve turned on all the logging stuff in settings but all i see in my logs is:

info ║ Dashboard URL: https://blah

I can’t find anyone else with this issue in the forums here which makes me think that I’ve missed something in my setup?

Seems to just be an issue on Windows Phone (and I guess that won’t be a problem for much longer… :()

Working fine on Android!