Ubiquiti UDM PRO - Load Balancing

I have around 10 Residential sites with UDM Pro and the Failover is not working as design. For the Failover to work I need to physically go and unplug the WAN1(port9).

I been looking for the Load Balancing feature but is not allowing me to change it from Failover in the settings.
Does any one have ran into this issue?