SPDIF = Sony/Phillips Digital Interface Format
Since it is a Sony soundbar, it should support the interface.
Make sure that you have connected the corresponding output and input jacks (SPDIF out on the PC to COAXIAL on the soundbar)
Make sure that you are indeed using a coaxial cable, not just a regular analog audio cable.
Are you sure that you selected the correct input using the remote control of the soundbar? It should be set to COAXIAL, not OPTICAL.