FortiGate Virtual Interfaces Shows as down on the GUI, but in CLI, the interface is UP.

Hi RJ1,

As you mentioned that the ISP goes down but still there were active route in the routing table. In FortiGate, the route preference will be first policy route and then SD-WAN routes.

Hence you should have a default route pointing toward the SD-WAN virtual interface this will help to route traffic with other interfaces when one link fails.

Please refer to the below article on how to configure an SD-WAN properly.

https://docs.fortinet.com/document/fortigate/7.6.0/administration-guide/218559/configuring-the-sd-wan-interface

For your query make sure:
1. Static route is pointing to SD WAN zone:

https://docs.fortinet.com/document/fortigate/7.6.0/administration-guide/626338/adding-a-static-route

2. Make sure the Performance SLA has the SD WAN members selected and 'update static route' enabled:

Note: If 'update static route' was disabled under Performance SLA then enabled the 'update static route' and check the routing table.

https://docs.fortinet.com/document/fortigate/7.6.0/administration-guide/723056/link-monitoring-and-failover

If you have found a solution, please like and accept it to make it easily accessible to others.

Regards,
Aman

Hi RJ1,
Can you please share the output of the CLI?
And GUI screenshot 

Hi RJ1,

If 'update static route' was disabled under Performance SLA then enabled the 'update static route' and check the routing table.