If you want a newsletter to start arriving back in your Inbox again, you might need to remove it from any Rollups first.
To do this, find the sender in the Subscription List and click the “Rollup” button. If you have multiple Rollups then remove the sender from each one (don’t forget to click save!).
Once the mail is no longer in any Rollups, you can click the “keep” button to make sure it will always land in your Inbox in future.