E-Con and Relinquished

Just playing ranked, got in a situation where my opponent had 450 lp and I had 250 lp, he only controlled an Embodiment of Apophis and I controlled a Relinquished equipped with his Leotaur. I drew into Enemy Controller, activated it intending to tribute my Relinquished and take control of his Embodiment and attack for game. I couldn't pick the second option for some reason, either not allowing me to tribute Relinquished or changing control of Apophis. I'm a level 1 judge and there seems no reason for me not to be able to do this. How could this come?