Cant add widget

When I try to add the widget, the following message appears:

Please make sure to connect your form to your email marketing provider and to select a thank you page.

The mailchimp API key has been added and verified, i even can select a list to subscribe to.Tried both behavior methods, display immediatly and direct. Tried to create a second form, but when adding the widget , the message shows, cant even select a form.

Am i forgetting something?