1.) My Emrakul, the World Anew (summoned by Loot, Exuberant Explorer) dies to a board wipe on opponents turn.

2.) next turn (my turn). +1 Wrenn and Seven, play a land (13 total), activate my Conduit of Worlds (Targeting Emrakul, the World Anew)

3.) Problem: Emrakul, the World Anew is grayed out, not highlited, not a valid cast.

4.) lose the game.

5.) sad.

Note: if there’s any speculation as to why the cast was considered invalid, please let me know.
-Thanks!