Mechtitan core not allowing me to make mechtitan
Playing on iPhone. I have the mana and available vehicles/creatures, yet it won’t let me use that ability. Lost me the game and wasted my time because of that.
You specifically need 4 other artifact creatures or vehicles. You only got two: the Peacewalker Colossus, and the Hotshot Mechanic. The four permanents to activate the ability have to be artifact - vehicles, or have to be artifact creatures (be both creature and artifact). Your Darksteel Citadel and your other creatures don't fulfil the criteria.