Audirvana

I've hooked up an optical from pc to the denon and it still doesn't detect the denon as a dac 

Do you have guest network? Generally when the 2 components are NOT on the same network, these issue happen. Make sure your Wireless and Ethernet network are the same. Or at the least your wifi is not connected to a guest network.

Just a thought, as it happens sometimes between my laptop connected to the ethernet and the iPad which is wirelessly connected.

Both are hard wired to the router, pc and denon