Play you tube videos through Hi fi system

[pm]

Have just decided to update my hi-fi system by purchase of Marantz PM6006 amplifier, I was attracted to this model due to it having 2 optical connections for my 4K LG43UF68OV Smart tv and Technics SL-PG500A cd player, the tv now plays through hi-fi, except when selecting a You Tube video, it will only play through tv speakers, and the optical blue light is flashing on the amplifier, most annoying, any ideas to the cause?

 

[spiny norman]

when selecting a You Tube video, it will only play through tv speakers, and the optical blue light is flashing on the amplifier, most annoying, any ideas to the cause?

Presumably with YouTube videos the TV is outputting an audio format the amp can't handle. This article suggests that may be the case.