Try starting Bitcoin Core manually. First start Armory. Then uncheck the "Let Armory run Bitcoin Core in the background" box in File > Settings. Then stop Armory. Start Bitcoin Core and let it sync and get fully started. Then start Armory. It should then say that you are online. Then you can send. If you are not online, you will not be able to send transactions.
I am bringing this topic in the present day so to give many thanks to achow101!
I have tried everything for solving connectivity issues with Armony and Core wallet but with no success.
In between my searching inside the forum I also found this old topic which actually gave me the solution
So I posted for helping other users that may have similar errors