Recommend to deploy a new OVA from 12.4.3 and import the older configuration to the new deployed 8200v appliance.
If you attempt to upgrade to SMA 12.4 from SMA 11.3 or earlier, the upgrade stops, and you get a message stating that you cannot upgrade from your current version.
You can upgrade a supported SMA 8200v appliance directly to version 12.4.3 from these versions:
Upgrading a virtual appliance hosted on ESXi requires network adapter changes.
To upgrade the 8200v Virtual Appliance by importing the configuration