Make sure that the optical cable is seated properly in the jack and the little rubber/plastic nub has been removed (sounds trivial, but it's a common mistake). It should click into place with just a little bit of force.
If all that is correct, then check if the mmc-1 (Emotiva?) is assignable and make sure that you've assigned the digital input to whatever input selector you want to use. Note that 'raw' should be the correct setting on the Oppo (although most players use the more descriptive term 'bitstream') - it means do not interpret the data, just send it out the optical output.