I have my TV connected to a computer via an HDMI cable. On the way to the TV, the cable goes through a HDMI Audio Extractor (TOSLink to AV Receiver).
I don't use this setup a lot, just occasionally when I record a TV show on the computer, but it has worked for months.
Now, the last two time I've booted up the computer, I don't get ANY sound from the computer to the TV (via the HDMI), or the AV Receiver (via the TOSLink), until I disconnect the power from the HDMI Audio Extractor and then plug it in again. (It took a lot of head scratching, and trial and error to figure it out the first time).
I have both the computer and the Extractor plugged into a power strip with a switch, so the when I power up the power strip, the Extractor powers on right away, then I turn on and boot up the computer. I don't think this should matter, since, as I've said, it's worked this way months until now.