Well three companies already have asked about an option to join this (or rather to be able to license the technology). The times of one simmer flying an airliner will soon be behind us and it can't happen fast enough.
Lets focus on your system
The WXR only displays precipitation (clouds are not equal to precipitation).. So if you don't see anything on your ND, I would assume there simply is no precipitation around you.
For test purpose just fire up your FSX with the stormy weather scenario, switch the ND range to maximum and enable the WXR (SYS switch to the left, all other WXR buttons and switches can remain in their default position). And of course don't forget to increase the TERR/WXR brightness via the outer ND brightness knob.
Now you should see something...