The plugin work fine if I enable a multi-list selection; don't work with a simple single checkbox. There is no new 'MailPoet' tab in the Gravity Forms settings page.
I use Gravity Forms 1.8.5, Gravity Forms PDF Extended 3.3.4, MailPoet Gravity Forms Add-on 2.0.0 and MailPoet 2.6.
Another question: I would like the checkbox cheched. Is it possible?