MultiWAN can only ping WAN on active gateway

[swb]

Have set up a few HA multi-wan opnsense boxes and have always been able to ping both WAN interfaces for monitoring using a floating ICMP rule.  On a new setup I can only ping the WAN interface with the active gateway i.e. by adjusting the tiering or weight to make the backup GW active I am then able to ping the interface but can no longer ping the primary.

Have checked the config with other sites able to ping both whether active or not and cannot see any difference, what would be preventing the ping response?

Thanks

[RenegadeTech]

Did you add gateways under System -> Gateways for each WAN? Did you set a gateway under "IPv4[v6] gateway rules" for each interface?