You needed to download the x0190 release of DoD and enable it in that version only. So if you didn't do that then you're out of luck until D* decides to enable a 'secret word' again to enable the feature.
Besides having the proper code on the HR20, D* also needs to enable your account to use DoD, they were doing this by monitoring which HR20's had their network connections active and CE sofware downloaded, so if you haven't network connected your HR20 I'd recommend that you do that ASAP so you'll be ready to go.