An update for anyone following this thread:
Yesterday I brought two different computers to the studio to test the ADX Core Cards in. The first is my current DAW which is built around an ASUS Z390a Prime motherboard. I built this machine late last year and it's running great. 32GB of RAM, RTX2060 graphics, all M.2 drives, and a FireWire card (because my interfaces are old). It is running Windows 10 Pro.
We tried both Core Cards in that machine and had a similar result; they pass DigiTest fine, show up in Device Manager with no issues, but ProTools doesn't see them. However, I could use them with Cubase and WaveLab using the Avid ASIO driver.
Then we tried my old DAW, the one that I replaced with the computer mentioned above. It is an ASUS Z97 motherboard with 32GB of RAM, a TI1070 GPU, and running Windows 7.
And to my surprise, the Core Cards were recognized (we tried both) and available to use in ProTools. It worked flawlessly without any trouble at all.
Now, both of the new computers (the one mentioned in this post that belongs to me, based around a Z390 mobo and the one mentioned in the original post that belongs to the studio based around a X299 mobo) have one common denominator: Even though they use different Intel chipsets (300 series and 200 series respectively), both chipsets support TB3 natively, which is why we bought them. I eventually would like to update my old interfaces to something new, preferably using TB3 for channel count and latency. And my friend who owns the studio wanted to be access some harddrives and possibly use another interface here and there.
Could it be that something in the implementation of Intel's Thunderbolt chipset or drivers is causing a conflict? It should be noted that Thunderbolt is turned off in BIOS on both machines under the ON-BOARD DEVICES menu. And yes, both computers have the latest chipset drivers installed.
To make matters even more confusing, if you look at Sweetwater Sound's professional PC offering, the CS450 computer for $2600, in the picture the motherboard is clearly that same ASUS Z390a Prime that I'm using in my computer. It is unmistakable. So if a company like SS is using that board for a professional DAW, it SHOULD work with HDX, right?