Colossus does not always appear in versus

BLR60

I'm new to the game but I have one 3 star hero, Colossus, and he does not always appear for 3 vs 3 fights. The other 16 characters are always available but not him. Is this a bug or am I doing something wrong?

Eb0ny-O-M4w

Maybe you are playing in the wrong arena ...
Some arenas only allow you to use 1 and 2-stars. Other arenas allow you to use 2 and 3-star, and other arenas allow you to use 3 and 4-stars and so on.