Why can't I use my Charizardite Y card/plate in Pokemon Duel?

My Charizardite Y card/plate is not working even if satisfies all the set conditions.

As you can see in the following picture, I have no Mega Evolved Pokemon and I also have a Charizard.

But as you can see in the following picture below, I am not able to use the Charizardite Y plate.

Why can't I use the plate?

Edit: I have also placed my Charizard in the field but even then I can't use my charizardite y card as you can see in the following picture

Solution 1:

Do you have a Charizard Y figure? To mega evolve, you need a Charizard figure, the Charizard Y plate, and a Charizard Y figure.

Solution 2:

The Charizardite Y card/plate text says "Choose one of your Charizard on the field..." Your Charizard is on the bench, not on the field. Move your Charizard onto the field and then use the plate.