Go to Campaign Settings → Integrations and API → Rewards tab and click Connect under the Tremendous tile to re-authenticate.
You will be redirected to Tremendous to authorise the connection. Click Authorize to confirm.
Once reconnected, go to the Rewards page and open the Issued Rewards tab. Look for any rewards with a Failed status badge — these are rewards that failed during the disconnect.
Re-issue failed rewards by clicking the three-dots action menu on the reward row and selecting Issue Now, or by selecting them in bulk.