After the 3.0 release, and major overhaul to the plugin, a few users reported receiving a fatal error upon activating the plugin. This was due to a missing php file, which played an integral part in connecting to the Mail Chimp API.
We have gone ahead and pushed out a 3.0.1 minor release, which adds in the missing file, and resolves the fatal error.
If you are still running an older version of the plugin, 2.2.1 or below, it is now safe to update to 3.0.1 without fear of issues.
Sorry to anyone that was affected by this issue.
https://wordpress.org/plugins/yikes-inc-easy-mailchimp-extender/
