Hey @Vernon,
This line of yours reveals an issue with your theme:
Additionally when reverting to the twentyfourteen theme it did in fact work
If it works fine in a default theme like Twenty Fourteen, but then simply activating your other theme breaks it, then your best bet here is to contact the theme developers of that theme for support.
I wish you the best of luck with that! If issues arise specific to our plugin, and the issues persist regardless of whether you are using the Twenty Fourteen theme or not, then that is a plugin issue so definitely come back and open a new thread 🙂
Cheers,
George