What is wrong.

I’m trying to play with my friend, I try to join his game and it says ‘‘The party may have an incompatible network setup. Your setting, OPEN NAT is usually compatible. Visit ww.halo4.com/nat for more information.’’ so I went to halo4.com/nat and I ran the test to see if anything was wrong with my NAT and it says everythings fine except it also says this. LIVE STATUS
Yellow ! Service: Service Alert. What does this mean, and is this preventing me from playing with my friend? What gives? :frowning: