Bandwidthd stopped graphing

I just installed bandwidthd-sqlite on a DWR-921. It worked initially but I need to save the stats between reboots.

I changed the /etc/config/bandwidthd file to read:

option promiscuous true
option output_cdf true

Now there's no graphing, no stats whatsoever.

I'm not an experienced user. Where do I start?

Thanks