A gateway is incorrectly marked offline

If a gateway is listed as offline, but the WAN is actually up, several things could be at fault:

• First, test to see if the monitor IP address responds to a ping from a client device on the LAN, and again from Diagnostics > Ping.

• If the device with the monitor IP address or other intermediate hop drops ICMP echo request packets without a payload, manual pings would work but the gateway monitoring would fail. set the payload to a value of 1 or higher.
• If the gateway or monitor IP address does not respond to ICMP echo requests, enter a different monitor IP address to use instead.
• If the monitor IP address is configured as a DNS server for a different WAN, the static routes could be causing a conflict and the echo requests to the gateway may not be following the expected path. Set a non-conflicting monitor IP address on the gateway.
• If there is an outbound NAT rule on the WAN with a Source of any, it can cause problems with traffic on the firewall, including monitoring traffic, because that will also NAT traffic from the firewall itself. This can be especially problematic if the source address is changed to a CARP VIP. Fix the outbound NAT.

If all else fails, it’s possible the circuit really is down, but the testing methodology appears to show it up. Verify the Interface and Gateway settings and run the test again, and try traceroute to make sure the traffic is leaving using the expected path.