No sound from Apple TV 4 to Onkyo amp

I have an Apple TV 4 connected via hdmi out to an hdmi input on an Onkyo TX-SR605, whose hdmi Out is connected to one of the hdmi inputs on a Vizio E70-E3 tv. I have stereo speakers and the Onkyo and ATV are both configured for stereo sound, not Dolby. The television is new, and this problem developed after about a week of use with the new television. The symptom is that I get video from the ATV displayed on the television, but there is no audio coming out of the amplifier to the speakers. When I connect the ATV hdmi cable directly to the tv I get video and sound. I have owned an Apple TV for years in this same configuration with a different television and have never had this problem for that entire time. I purchased the ATV4 shortly after it was released, and had a 2nd generation before that. Here is what I have tried: Cables Switching through all the hdmi cables I own using direct connections from the ATV to the television to verify that there are no cable issues. Regardless of the cable I use, when connected directly to the television, I get video and sound. Regardless of the cable used to connect from the ATV to the amplifier, when connected through the amplifier I get no sound. Initialization Order: I’ve tried all permutations of tv/amp/ATV power on sequencing, and it makes no difference. No matter what the power-on order is, I never get sound to my speakers when the ATV is connected to the amp. Onkyo Listening Mode The Onkyo has a number of different listening modes, some Dolby, some not. I have cycled through all the different modes with the same results. The normal listening mode that has worked for the last 4 years or so is stereo. Apple TV resolution and audio configuration I have tried changing the resolution and refresh rate on the Apple TV and changing the audio configration to different settings, but no setting change has made any difference. The current setup is to use a resolution of 1080p with a 60Hz refresh rate, and stereo audio configuration. The only suggestion I have found but not tried is this one: http://www.pooraudiophile.com/2013/12/the-fix-for-appletv-hdmi-woes-and-hdmi.htm l ...but I really am not interested in spending $100 to solve this problem, or to find out that it doesn’t solve the problem anyway. Please help with some troubleshooting suggestions for this problem that don’t involve purchasing more AV hardware.