Recently I purchased a Fenvi intel AX200 WiFi and Bluetooth PCIe Card, However even after installing the drivers from the Intel website WiFi didn't seem to work although Bluetooth works fine. The product doesn't even show up in the device manager with an unhidden view. I am using an HP ProDesk 400 G6 running the latest version of Windows 10 with the latest BIOS update. I currently do not have a GPU installed.
16 GB DDR4 2666 RAM
intel 660P NVMe 512GB SSD
1TB WD BLUE 3.5" HDD
Win 10 Pro 64
According to the specifications of the HP ProDesk 400 G6 there are multiple PCIe slots. From what you are describing, the Fenvi AX200 adapter may not be installed in the proper slot. Try moving the network adapter to a different slot.
Additionally, I would recommend using the driver directly from Fenvi for your adapter. Using the picture you provided combined with the name, I found a driver located on this page from Fenvi: http://en.fenvi.com/en/download_zx.php?s=4&page=2