settings on my Hegel cdp

Hello all-

I am having a bit of trouble with my set up and wonder if you all had any advice.

I recently purchased a Hegel Viking cd player.  I am running RCA cables from the cd player to my amp that powers my speakers.  Sounds great.  I also have a BNC cable from the digital out on the back of the Viking connected to a Schiit Bifrost DAC connected to a LYR 2 amp for headphones.  I used this same setup with my prior cd player (Line Magnetic 515).  I don’t get any sound with the Hegel out of the headphone amp, however.  I sent the headphone amp in for service (it’s fine); I have new tubes.  I’m thinking of getting a new BNC cable in case that has failed (but it isn’t that old).  But is there some setting on the Hegel that I need to select for it to know to send music to the external DAC when I use my headphones?  I see a “DAC + “ button on the remote?  The manual says this is for "DAC input."  I don't know what that means.  Do I need to do something with this to select the external DAC?

Other ideas?

Many thanks!

Margot