Enable IPTraffic (per IP monitoring) button is not working

[ashtree]

I have the ac66u and just installed this firmware (380.64) but the radio button to turn on "Enable IPTraffic (per IP monitoring)" does not work. I tried to select the USB drive under "Traffic history location" but the USB is not seem in the drop down menu. This is even though the USB drive is seen in the network map.

Any tips to get this bandwidth monitoring by device working would be much appreciated. This feature is the reason I installed this firmware.