Hi Jerry,
I subscribe to the GitHub FlexASIO mailing list, and I read the conversation you had with Etienne. This part:
seems to suggest a possible HDMI audio driver issue, since you can't ping all channels in Device Manager even without using FlexASIO. It's weird that ASIO4All works though. Anyway, if I recall correctly, you have an Acer laptop that's similar to mine. On mine, I went into Device Manager and right-clicked on "Intel Display Audio" under "Sound, video and game controllers." When I chose to update the driver, it told me I already had the latest one. But it seems Windows doesn't do such a great job of finding the latest drivers. After doing some searching, I ended up going to
this page to try to find the latest driver. I wasn't sure if that was the correct one for my hardware though, but at the top of the page, there was a banner saying "Automatically update your drivers" with a "Get Started" button. Choosing this downloads the Intel "Driver & Support Assistant" application.
When you run this app, it launches your browser, goes to their website and scans your system, telling you the Intel drivers that need updating. For each such driver, it shows a "Download" button. If you click that, it has this obnoxious behavior of downloading some unknown installer file to an unknown location, then executing it. I hate that kind of "behind the scenes" operation, but there is a workaround. You can click the down-facing caret in the driver description, and this reveals a previously-hidden "view details" link. I right-clicked that to open it up in a new browser tab. This took me to a page that showed the actual driver install file, which could then be downloaded and run manually. I like that approach much better, as it gives the ability to save the file where I want, and know what I'm downloading. I just had to make sure to choose the 64-bit version, as both it and the 32-bit drivers are shown on the page.
Anyway, the Driver & Support Assistant found a more recent video driver that Windows couldn't find. According to the Intel docs, the HDMI audio driver is contained within this video driver (see
here and
here.) They're not separate like with AMD. This successfully updated my driver, but I can't test it with REW, as I don't use an AVR or pre-pro in my system. My system uses an 8-channel USB device (Tascam US-16x08). I use FlexASIO with it, and all channels are accessible. I did hook up a spare HDMI monitor to my laptop and got sound out of it with the newly-installed driver, but that's all the testing I was able to do.
Interestingly, when I go to the Acer web page that has the drivers for my laptop, there isn't even any Intel video driver listed there. There may be some default one that comes with Windows, and Windows apparently isn't able to find a newer one for some reason.
Might be worth a try. The Intel Driver & Support Assistant seems pretty handy.