TOPIC: Registration plugin - Interest Group dropdown

Hi all,
I installed CMC on a Joomla 3.5.1 site. I'm trying to configure the Registration plugin: everything works fine exept if i try to select on the "Interests" field a Group created as a dropdown on the Mailchimp backend. If I try with "Radio Group" or a "Checkbox Group" everything works and I can see it on my registration form, but when a try to create a group as a dropdown, I cannot find it on my registration form...
I really have no clues...
Please help me!!

So what happens in the form when you have a dropdown? Is the form broken or is just the dropdown missing?

Regards,
Daniel

The form seems to work right, only the dropdown is missing.
Thank you for your help!