Hi There,
I have had a similar issue with other products. The solution I found was to simply turn the volume right down on the app and then back up again. This fixes it every time. Not a great fix and clearly some kind of bug but at least it gets it to play.
Hope this helps.
M
I’ve not had a chance to try it for a while I’m afraid, as we’re not currently using the optical input. I will be setting that up in the next few months though and will report back when I do.