I'm not real familiar with the Denon receivers, their menus, or their manuals, so I may not be entirely correct here. I think that the "Manual Setup" | "HDMI Setup" | "i/p Scaler" option needs to be set to either "A to H" or "A to H & H to H" for analog video inputs to be output via HDMI. The "Video Select" and "Video Convert" options under "Source Select" | "<INPUT NAME>" | "Other" may also apply, though.

Man, that is one unpleasant manual...