sign-up form doesn't work

Hi Alessandra - welcome to the community and thank you for your question! 

Are you able to provide more details, so that we can troubleshoot your issue?  (screenshots to accompany the info are always very helpful!)

• is your Button Click Action configured to subscribe users to a list? which list? (see screenshot example below)
• do you have double opt-in activated?  (if so, users should receive a confirmation email which must be clicked in order for the user to be subscribed)