It's not only you. During the Trinity Gate Campaign Mission, I gain the ability to build Ion Canon Frigates, but they don't build. I was able to queue them up while paused, but the queue disappears when I un-pause the game. When I made it to the next campaign mission, it suddenly worked. It's definitely a bug, and I am trying to see if it's an issue with my fleet, or if its the mission that is bugged.

thanks for confirming, it's strange they did not catch it during QA testing