Aim Down Sights - 2 Issues

I am playing on PC and have had 2 separate issues where I cannot aim down sights. One is while playing the Campain, set on Hardcore dificulty,  on Mission 2 (The Rock), cannot ADS.

The other is while playing Multiplayer on Breakthrough, while playing as Support, with the USG-90 equiped with the 1.50x sight, cannot ADS.

Very annoying...