This is not Google+ directly, so I'm not sure if the answer for Google+ is relevant.
Where should I report a bug relating to Google +1 button
google-plus-1
google-plus-1
This is not Google+ directly, so I'm not sure if the answer for Google+ is relevant.
Best Answer
From Webmaster Central on Google Product Forums, filtered for “Google +1 button” category.
So in my opinion, you can either use these forums or the Send feedback form from Google+ pages.