You were right & I was wrong, its cause its tier, IX, normally you don't get to have accelerated crew training cause you have to research the next vehicle to do so, which is why it wasn't earning anything. It is now, they gave me the accelerated training when they moved me up, don't know why, but I still have to earn enough Exp to research the Sheridan.
This is what confused me. Now it is earning credits. Yayyy
I was wrong, you were right so thank you for sticking to your guns, it made me think this through & now I get it.