I've been reading some threads elsewhere, I've checked the end of the TOSlink, there is a red light, yet my 568 outputs nothing on the LD (laser disc) which is suppose to be the optical input (TOSlink).
The source labelled inputs and physical inputs are completely configurable.
Unless you know for sure (ie you set it up like that either via programming it or setting to a standard type) what source label is connected to, then you probably want to try other source labels or retype to a known good configuration - later will lose customisations and settings. Don't assume that LD is the source for optical.