Invalid attempt to add a lead

This plugin seems to have everything I need, except that I can’t get it to add a lead/contact into Hubspot.

I followed the directions, but get the response ‘Invalid attempt to add a lead’ every time.

I’ve tried with multiple forms, with no luck.

Any help or updates on this would be appreciated.

http://wordpress.org/extend/plugins/hubspot-for-gravity-forms/