I had Seymour Guado and Gogo, Master of Mimicry on the battlefield. I had full control mode on. I activated Seymour’s ability for 7 mana, I had 3 untapped lands left. I tried activating gogo (he was not summoning sick), and I could not activate him (should have been able to pay 2 mana for the x x cost). This cost me the 4000 gem sealed event. This has not been the first time I was unable to activate gogo in a game!