The version of ONTAP in your case is a minor-version of 9, which is 7.3.1 (or earlier). We support 7.3.3 or greater (it has to at least be an API minor-version of 11). The net-ifconfig-get API call wasn't supported with earlier API calls which meant we couldn't figure out where the VMware Datastores were being mounted from based on the network configuration (for NFS). As a result we required at least an API version of 11 so the API call we needed was available.
You can test this on your controllers by using the command:
priv set -q advanced ; ontapi execute "<net-ifconfig-get></net-ifconfig-get>"
This would tell you if you can run VIBE based on your existing 7.3 version level. If the API call isn't listed (you see the message "Unable to find API"), it isn't supported.