On the SR805, only Optical or Coax In can be routed to Optical Out. That is probably why the receiver is not able to send signal.
The Oppo Optical Out should be no issue. Most likely, you need to select the correct output setting and vice versa, the correct input setting on the sound card. (Also, make sure you're using the Claro Halo Optical In and not the Optical Out by mistake. Happens to be best of us, your's truly included.)