Did you connect antenna to the AX201 board you installed?  by default Dell 7090 config does not include wireless M.2 card (and antenna).  if you add the wireless card you also need to get antenna for it.   [IMAGE] [IMAGE]    
I have installed the AX201 board on a Dell Optiplex 7090. Windows 10 detected it and both wifi and Bluetooth appear to be working properly according to Device Manager. When trying to connect to wifi networks there are none found! I have another desktop, a laptop and my mobile phone all located very close and they can all can find several wifi networks. The same with Bluetooth. When trying to add a new device (eg speaker) there is again nothing found although the same device is discovered by the other desktop, laptop and mobile phone.   I have tried several times to delete the drivers and install in turn drivers downloaded from Intel, Dell and Microsoft (older and newer) all installing successfully but with no success regarding finding wifi networks or BT devices. Device status always indicates that the device is working properly (no yellow triangle).   I have also updated the BIOS to the latest version and all other drivers suggested by Dell. The AX201 has never worked.
Intel AX201 not working on Dell Optiplex