HDMI to SDI mini converter WD TV

I am taking WD TV Live hub HDMI output into a Blackmagic HDMI to SDI mini converter. Then into a ZeeVee HDB 2620. If the micro switch 1 is in the on position, down converting to 480i, then I can see the channel. If I turn micro switch 1 to off, all I see is the ZeeVee test pattern. The SDI lock on the modulator is lit in both configurations. I connected my computer to the blackmagic via HDMI and I can get a 1080p output from the Zeevee. Any idea why the WD TV box and the blackmagic aren't getting along?
Thanks.