MailChimp

Check your server with FTP to make sure the plugins folder is not empty.

And other than deactivating and reactivating the plugin

or deleting and reinstalling the plugin.

(You may lose some of the plugin data or settings.)

I’m not sure what’s happening.

FTP is a File Transfer Protocol program used to send files to a remote server.

You can also look on your web host cpanel under files.