There are two mods that come with GWX that could cause this problem.
They are
GWX - Indian Ocean Campaign Files Only
GWX - Black Sea Campaign Files Only
You didn't activate either of these by any chance?
Doing so will remove
all the traffic from everywhere in the world except either the Indian Ocean or the Black Sea. They are designed to cut down on loading times if you are operating in those theatres only.
EDIT: ps. welcome aboard