This might be the reason.
You should make sure to always keep your software up-to-date.
Not that this will only guarantee you compatibility, but newer versions also contain bugfixes and security- or performance-improvements.

Make sure to get Armory 0.96.4 (https://btcarmory.com/0.96.4-release/) and core 0.16.2 (https://bitcoin.org/en/download).