You probably need to assign a digital input to whatever analog input you have connected the LD player to.
Assuming this is a Pioneer, VSX-1020-K, these are the default assignments of the digital ins (black dots represent what analog inputs can be assigned a digital input)….
If you have the manual for your AV Receiver, pages 40 & 41 explain how to adjust the assignments or simply match up what the chart says.
Hope this helps.