question

That error means that the ARN doesn't match what SNS expects for the device you're trying to send a Push to. The sync between the various pieces of the puzzle for the platforms is sensitive to any changes, so it's possible something's out of sync. If, for example, you registered for Push on the device but then later updated your ARN, they wouldn't be in sync anymore and you'd have to re-register the device for Push. Try stepping through the setup from the top, to see if that syncs things back up. If not, please email the details of your title, and the calls you made (including the platform and Key/Credential used) to devrel@playfab.com.