Hi kailibuy,
Thank you very much for the cooperation, yes, you are right. I have to test on my site first to see if the problem is only due to the plugin or not. As you know, this is a function of sending and receiving, it means the process includes other parites: your hosting server and mailchimp. Sometimes, in case the problem comes from other parties, we also need contact other parities.
Yes, i will reply to you as soon as possible getting the answer based on the responder function.
About the mailchimp, The list tab on the mailchimp site updates the new information slower than the function of account, so i want you try checking the account information related to subscribers first.
Can you try the following steps.
1.After submitting a form
2.you come back to your mailchimp account and click on account ; https://i.imgur.com/SHrfdXC.png
3. Scroll down and check whether or not the counting of subscriber is increasing : https://i.imgur.com/6Y4Gawd.png
Sincerely,
WR support team