I can think of a couple possible fixes:
1. Make sure the DR16's mixer is set to 'multi'. To do this, press SUBMENU, then MIXER. Use the joghweel to spin down to SETUP. Now shuttle over to toggle between MULT and MIX. MULT is what you want. MIX routes everything out the stereo/AES outs.
2. You can also flip the TDIF output to either 1-8 or 9-16. Follow the above instructions except jog one further to TDIF.
Use the shuttle wheel to toggle between NORM and SWAP.
On the DA7, go to the D-I/O page to confirm the DA7 is seeing the TDIF card. If you're using slot 3, make sure you've switched the source for inputs 9-14/15-16 to SLOT 3, not ANALOGIN9-16.
Hope this helps. Feel free to email me privately if there are any other questions.
Andy