To resolve the issue, perform the below steps:
1. Delete any current cluster configurations from this appliance
a. This step only applies if cluster configuration exists
2. Ensure that both appliances have the correct UTC time set ( /admin interface | System Status/Settings | Date/Time Configuration | System Date )
3. Restart both appliances ( /admin interface | Shutdown | Tick Restart and click Shutdown )
4. Re-attempt the enrollment