Hey there, as others have mentioned, it could be a case of those Champions still being on a cool-down if they were used in an arena recently. If needed, you can also reach out to our Support Team and let them know about the issue.
You can contact them from the game's home screen by clicking the gear-shaped icon in the top-left corner and then scrolling down to the button labeled "Support". They can also be reached here.
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You can contact them from the game's home screen by clicking the gear-shaped icon in the top-left corner and then scrolling down to the button labeled "Support". They can also be reached here.