I haven't flown the PMDG 777 for a while since I updated Active Sky Next to the latest update, Now I am in a middle of a flight and turn on the weather radar like usual, and I get an x on the MFD.

 

 

Now I am in a middle of a flight and turn on the weather radar like usual

As an aside, you should turn the radar on before departure and turn the radar off after landing. This procedure and not a solution.

 

 

I get an x on the MFD

 

Not sure what you mean by MFD since all the DUs strictly speaking are multifunction displays.  Are you referring to the ND navigation display where radar is normally displayed? Was this a green x or red x? Did it clear when you turned off the WXR Radar? You using the EFIS panel to turn radar on/off?

Have you checked that ASN is effectively connected to FSX? (check it in the lower border of the ASN window).

Sometimes on my computer after a crash when leaving fsx, ASN doesn't connect automatically when I launch fsx again and I have to reboot ASN.

 

Also, what happens when you perform the weather radar test?