I’m having the exact same problem as stated in this post from December, which as far as I can see, has never been solved.
Just as in this post, everything else is green except for live server, I can’t contact ATC, and I’m not shown on LiveFlight. The problem started about halfway through my current flight from KSEA-KIAH (on the expert server). I’m still flying now offline though. I’m using an iPad Mini 2 with the current iOS and Infinite Flight, which typically runs the app great. If anyone has any tips they’d be appreciated!