I am playing Omega Ruby and have given my Charizard a Charizardite X. Despite this, when I go into the battle, I am unable to click the mega evolution button. It appears on the screen, but if I press the mega evolution button, and do a move. The Charizard will not mega evolve. If it matters at all, I have not beaten the Elite Four yet.
Okay, after some thought and experimenting, I have deemed the cause to be the mega evolution of a second Pokemon during the same battle. Example: Mega Evolving a Lucario but then not being able to Mega Evolve a Sceptile when the Lucario faints in the same Pokemon battle. thanks for helping all.