If Multi VDOM configuration is enabled on Fortigate firewall Solarwinds ipam couldnt discover Fortigate VDOM subnets
beacouse device is responding only physical firewall information by using OIDs from solrawinds documantation.
https://documentation.solarwinds.com/en/Success_Center/IPAM/Content/IPAM-Import-IPv4-subnets-and-IP-addresses.htm
If you need to discover Fortigate VDOM subnets you should use different OIDs
example:OID: 1.3.6.1.2.1.4.20.1.3 gathering Fortigate VDOM subnets
Becouse of Solarwinds is not using OIDs different then documantation Fortigate VDOM subnets couldnt be discovered.