I'm having the same issue.
You don't seem to be alone...https://forums.playcontestofchampions.com/en/discussion/364189/auto-fight-bug#latesthttps://forums.playcontestofchampions.com/en/discussion/363861/autoplay-doesnt-enter-fights-very-broken#latestWhat device are you using? I don't have any issues on iOS.Someone said it only happens with 1* champs...