If an interface is configured with a static IP address using the Opengear config (say the lan port), but the interface is down due to cable unplugged/disconnected (but port is enabled/admin up), then NAPALM reports no IP address for the interface.
My best guess is related to this issue https://bbs.archlinux.org/viewtopic.php?id=294137 and either the default ConfigureWithoutCarrier= setting, or a similar issue.
It might be better/good to also check the Opengear config for the interfaces in case of statically set IPs.