AppleTV Wireless Audio Sync "No Tones Detected"

This on an AppleTV 4 Running TVOS 17.4 and a Samsung "smart" TV and Samsung soundbar. The soundbar is connected to the TV via an optical cable.

I've had this combination of gear for several years now and have never had audio issues. But, starting this morning the audio is out of sync with the video, no matter what app I'm running: AppleTV+, YouTube, Netflix, etc.

I tried running Wireless Audio Sync, but all I get is "no tones detected" in spite of the fact that the volume is quite loud. The iPhone is a 14 Pro running 17.4.

I've tried changing the Audio Format. The choices were Dolby 5.1 and Stereo. Neither of those helped the sync problem.

I can't understand how this happened as I am here alone and have changed no settings on the Apple TV, or the TV or soundbar. The AppleTV and iPhone are on the same WiFi network.

Any ideas?