Hi ,
When you try to fail over the box to the other one by disabling the Network connection but you still have the failover console cable connected it will not fail over. So if you want to test the fail-over first remove the fail-over console cable and then try this by switching off the Active unit.
With your current configuration the two boxes are synced? The Active/standby configuration is done properly? the active box and the stand by box shows their proper status? If all the configuration is fine and the two boxes are properly synced only then the fail over will work. It will be better if you can share the configuration that you have done or u want to do.
Regards,