PenciDesign replied
Hi,
1/ Seem you're using wrong plugin for MailChimp, please deactivate it and go to Appearance > Install Plugins > install plugin MailChimp for Wordpress
After that, please check guide for it here
2/ Please try deactivate all plugins and check it again.
After it work, let's enable each plugin to check what plugin caused this issue.
Best Regards,
PenciDesign