MissingReferenceException When "Reviving" After Ad

So the way my game works is when the player dies, you have the option to watch an ad, and upon completion, the player is revived. It works for the first time you play the game, but once you return to the main menu and replay the game, the ads still play, but the player doesn't get revived. alt textGives a MissingReferenceException saying a GameObject is null. When I check if the GameObject they're referring to is still there, it is. So where's the problem coming from?