Sunfire theatre grand processor 2 optical connections?

Looking for some help troubleshooting a new to me sunfire tgp2 receiver.

Hooking up a Chromecast hifi over toslink optical.  The receiver will switch on with the signal activation, and select the right input, but alas no sound is coming out.  Confirmed same across all three optical ins.

phono and fm work normally.

hoping someone familiar with this processor can help.

thanks