WordPress BigMailChimp pluggin caused conflict with Contact forms
I tried multiple Contact forms and none of them would display Thank You message or redirect to a Thank You page. Forms were submitting data just fine as I got all the emails (sender and admin emails).
So… I began to disable other plugins to see if the conflict would be solved. Lucky me! The first plugin I disabled was BigMailChimp – a signup form plugin and with it gone, everything was fine.