Hello,
Lots of times in IE11, Chrome and Mozilla on the first submit of e-mail address the form does not show Thank you message. I tested the module on Joomla 3.3 with CMC - Mailchimp 1.5 , the same thing happens on joomla 3.4.8 and CMC - Mailchimp 2.0.
I have just the e-mail field and submit. The button greys aout, disabling clicking and re-entering and stays like that. Sometimes you can see the users in the back-end as applied, but sometimes it does not display a user at all.
Thanks for your answer.