Failover Identity does not revert back to primary identity after connection is re-established

1. user_failover_identity - The index of the failover Identity 
2. retry_after_failed_register -  Number of seconds after a failed registration the Primary will try to re-register
3. active_line - The Primary Identity
4. user_expiry -  The proposed expiry time of the registration in seconds for line x. Upon expiration of the registration, the phone will send a fresh re-registration request. 
5. sip_health_check - Enables/Disables the status polling of primary server if the phone has been failed over to the backup server

6. session_timer - Session Timer for calls (try setting to 1800 seconds)
   

Be sure not to use Identity 1 as the Primary with Identity 12 as the failover Identity. There is a known issue (SCPP-6267 - Failover not working between Identity 1 and 12)

Retry and test the failover.