I own a Z390-A and just returned the EX3 card to MicroCenter. It WILL NOT show up in Device Manager or support the devices I plugged into it.
I followed the manufacturer's directions to install the included software prior to mounting the card. The card was properly seated and header connected to M/B.
The docs for the card on Asus' website do not indicate compatibility with this m/b. However, the web page for the m/b does indicate this card as compatible.
The rest of my rig includes a new i9-9900K, 64GB RAM, EVGA RTX-2070 (I'm a video editor, not a gamer). I use Win10/64Bit at the latest version.
My belief is that this is the correct card but that Asus simply doesn't have a driver for it that works with the board. I spent THREE...