Form submissions not being added to MailChimp

Please go to MC4WP > Other, and set it to “Log everything” (instead of logging only errors). Then test the form again. What do you see in the log?

Under MC4WP > Form > Settings, is Double op in set to Yes?
If so, the subscriber has to click the link in the opt-in email before it’s added to the audience.

Thanks for letting me know.