If you're using the balanced audio inputs in bypass mode there is no facility to enable subwoofer playback, as the bypass mode does just that, bypass all signal processing save for volume control and goes directly to the output.
If you do wish to enable subwoofer output for stereo sources, it will require using DSP on the balanced inputs, and you should be able to select Stereo for the DSP mode, and in the speaker setup your speaker configuration would be Front speakers as Large, and subwoofer set to Yes with Enhanced Bass also enabled. The enhanced bass will send a duplicate of the bass information that is sent to the full-range front speakers to the subwoofer as well, in order to allow the subwoofer to play when using a 2 channel source.
Hopefully that will do the trick for you.
Dave
If you do wish to enable subwoofer output for stereo sources, it will require using DSP on the balanced inputs, and you should be able to select Stereo for the DSP mode, and in the speaker setup your speaker configuration would be Front speakers as Large, and subwoofer set to Yes with Enhanced Bass also enabled. The enhanced bass will send a duplicate of the bass information that is sent to the full-range front speakers to the subwoofer as well, in order to allow the subwoofer to play when using a 2 channel source.
Hopefully that will do the trick for you.
Dave