Trouble connecting MailChimp

Hi, I’ve some problems trying to enable MailChimp using GoToMEETING (not Webinar).
I’ve set a shortcode on my website to have a form that works correctly, but I can’t collect data into MailChimp Account, even if I set up it correctly with user, password, API Key and list NAME (I’ve also try with list code ID).
Can you kindly help me?
Thanks a lot,
Roberto