Error: You have an older version of the Premium plugin.
If you are seeing this error message on your MailPoet admin pages and there is no update available for the MailPoet Premium plugin on the Plugins page, then you must deactivate and delete your Premium plugin in order to install the new version.
Deactivating and deleting the MailPoet Premium plugin won't make you lose any data from your MailPoet, rest assured.
After deleting it, you'll need to install the Premium plugin again by re-verifying your Activation Key on the Settings page. Here's how: Instructions to Activate your MailPoet Key.
This process will force MailPoet to download the latest version of the MailPoet Premium plugin automatically.