Lack of Surround Sound Signal from TV to Processor... Why?

Sorry, OP for the incomplete advice. I use my optical out from my LG OLED for 2.0 channel output only, (when I want to stream Youtube videos, Tiny Desk, etc....). That way I can place the TV output through my 2.0 Hi-fi system, bypassing the AV receiver. Goes like this: optical out (2.0) to Schitt Mani Dac to Prima Luna preamp to either mono tube preamps or SS amp (depends on the music) to a pair of Maggie 1.7is. For TV and movies I use an HDMI eARC out to a Denon AVR which uses a pass-through on the Prima Luna then out to the SS (Parasound A21+) which handles the center channel and surrounds, but uses the Maggie’s L&R for fronts. So, I should have said I prefer the optical as 2.0, but the other posters are right, you can certainly use your optical as your surround output cable. I just like to keep the two systems as independent as possible since I have no choice but to hybrid them.

@freediver 

Yes, I stand corrected:

https://www.google.com/search?q=toslink+support+multichannel+output%3F

Well...

freediver hit the nail on the head.  I dug into the "Advanced Settings" menu and there in front of me were the options; PCM, Auto and Pass Through.  It was set to PCM.  I tried Auto and Pass Through.  BOTH are providing 5.1 information to the processor!  All is well....  Big relief here!

Many thanks to freediver and everyone else who chimed in with suggestions.  Your suggestions, ideas and/or recommendations mean a lot to me.  Stay safe out there...

I’m running a HDMI from the tv to a 5.2 receiver.  Works like a charm.

I had the same problem when I connected a Toslink cable. Check your optical TV output to make sure that it is set to pass through. Otherwise, it will only output 2 channel sound. Check the processor settings as well to make sure that it is set to pass through. Hope this helps. 

Try borrowing a newish AVR with all channel preamp out…a Yamaha, Denon, Sony or similar, with HDMI 2.0, and see if that doesn’t solve your problem.  The TV probably puts out surround sound only via eARC, and you don’t have it!

@audiodidact that is totally INCORRECT..
 Toslink supports 5.1 as well as 7.1 Dolby Digital & DTS..

OP, are you saying your outputting from your TV with optical cable, not HDMI?  If that is the case (I certainly could have missed something in your post but...)  you can only get 2.0 from optical.  You need HDMI for multichannel sound.  And you go out from your TV to your receiver/processor (arc hdmi).  

Digging around the net it looks like there is an "Advanced Settings"in the "Sound" menu..Check it & see if you need to turn something on in there to activate Digital or 5.1 out..If that fails I would follow @sls883 advice & try another Toslink cable..If that still doesn’t do it,then yes a call to LG Tech Support would be my next move..Good luck..

Have you tried a different optical cable? Probably not it, but worth checking. 

I'm wondering if the newer Dolby Digital format is not recognized by your processor.... maybe someone smarter than me will chime in. 

freediver,

Thank you very much for your response.  My TV sound menu is slightly different than what is in the video (I think it is a newer version) but I understand the options.  I have tried selecting both of the the optical (TOS link) options with the same results (otherwise there would be no sound at all...).  One is simply the optical output alone and the other allows you to keep the TV speakers active as well.  I have no idea why anyone would want to do this (I could mute the TV speaker if it worked) but I tried them both. 

The processor has indicator lights to show the incoming signal; Dolby Digital, DTS and PCM.  Optical cables are supposed to support Dolby Digital, DTS and PCM so I think everything is OK when considering the processor.  The processor is showing the signal coming from the TV as a PCM (pulse Code Modulation) signal.  The TV just doesn't seem to output any Dolby Digital signals (5.1) no matter the source material for the TV.  Every setting I try with the TV results in a PCM signal. 

The surround processor manual tells me that PCM 44.1Khz supports both 5.1 and Pro Logic.  On the other hand the chart shows that PCM 96 Khz supports neither.  I figure the signal must be 44.1Khz (there is no indication) because Pro Logic works..

Maybe I need to contact LG tech support....  

Any other ideas?

By the way, the processor is an oldie but a goodie.  It is a California Audio Labs CL-2500 SSP.  I also have the matching amplifier, the CL-2500 MCA.  The MCA was (and might still be) the most powerful 5 channel amp on the planet with all five channels capable of 500 watts.  The main speakers are B&W 801 Nautilus (with a matching Nautilus center channel and a pair of B&W rear speakers) and twin Velodyne DD-15 subwoofers.  It is very annoying not being able to drive the system in 5.1.  Very annoying to say the least!  :(

I definitely appreciate your knowledge and thoughts about this situation!

The most likely candidate would be:
The Sound Output of the tv is simply not set to output a Digital signal..
https://youtu.be/HUAVERW3WMM?si=8TOg4aapSlRgzr-f............
Or:The surround processor audio settings are set to PMC 2.0 & not Digital...Hope this helps..