Each time from a long time ago and many Bitcoin Core versions and also many Armory versions I always got this message when I try to use «Tools -> Broadcast Raw Transaction...» from the menu.

Window title: Not Online.
Message: Bitcoin Core is not available, so Armory will not be able to broadcast any transactions for you.

Current versions:
Bitcoin Core 15.1
Armory 0.96.3.922 (armory_0.96.3.992-gcc5.4_amd64.deb)

I've been able to use all features I needed in Armory less this one. It's not a big problem for me as I solve this with bitcoin-cli. I think there's something wrong, because armory itself says it is connected to bitcoind and running fine, but it also says that it cannot broadcast because Bitcoin Core is not available...