EdgeWorker's may fail to execute the first time they are run on an EdgeServer. This step configures an automatic retry in the event of such a failure. 
Important Note 1 - For error handling to execute, the rule must be positioned after the CrowdHandler EdgeWorker rule that you created in Step 2. You can drag the position of the rule to the bottom of the rules list from the property manager editor screen.
Important Note 2 - The described error handling is designed to continuously attempt to retry CrowdHandler edge code in the unlikely event of a failure. If instead, you would like failed requests to retry AND bypass CrowdHandler altogether, you should contact your account team or send an email to [email protected]

https://techdocs.akamai.com/edgeworkers/docs/site-failover
  1. Select "Add Rule".
  2. Select "Blank Rule Template"
  3. Name - CrowdHandler Error Handler.
  4. Configure as shown below then save.

Criteria

Add Behaviour - Site Failover

5.) Continue to Step 6 - Activation