WDM updates the status to Imageable when the devices boot and do a DHCP request for PXE imaging. If the IP Helpers are in place to support PXE imaging, then the DHCP request will make it to WDM. If not, then WDM will not be ware of the PXE request and can’t set the device to imageable (PXE=Yes).
I would reboot the devices and see if they update.
If they still don’t update then see what subnet they are on and verify IP Helpers are in place to point to the WDM IP (if on a different subnet than WDM)
Also, wireless devices will never appear as PXE capable as there isn’t a UNDI driver for wireless adaptors (this applies to all PXE servers not just WDM)
-karaziel