Go to your WordPress Admin > Users page. if you don’t see the ‘grabpress’ user, then you must have deleted or renamed it since you installed the plugin.
If you’re not worried about having to set up your feeds again, it might be easier to just uninstall, and reinstall GrabPress and start from scratch. If it will take you more times to set up your Autoposter feeds again, you can just add the ‘grabpress’ user back in to your WordPress users list.
If the ‘grabpress’ user does not exist, you can just add the user back in to your WordPress users list. Make sure the user has Administrator or Editor privileges, and make sure the password is your API key (which you can copy from your GrabPress Autoposter page). The email address can just be fake, such as [email protected]. This WordPress account is what allows the GrabPress Autoposter backend to send new posts (based on your feeds’ requirements) to your posts (or drafts folder).
Let us know if you still have questions. Thanks.