First thing you want to do is to make sure there are no errors on the capture ports. Check the counters on eth2 and eth3 using the ifconfig command. ethtool -S <eth#> (where <eth#> is the interface you are checking) will give more detailed stats.
If (or when) there are no errors there then you may want to have a look at how what traffic is arriving at the Monitor capture port. Have a look at https://kc.mcafee.com/corporate/index?page=content&id=KB74074 on how to obtain a packet capture at the appliance.
That should help you get started.