Contact support if the Campaign is "out of keys".
You can use LurkBot at the bottom right of your screen to contact support if a Campaign is "Out of Keys".
If a Campaign you have been invited to is "Out of Keys", please contact our support so we can try to forward the issue to the Game Studio and check if they can add more keys to it.
Unfortunately, it is not guaranteed that this can happen as this is up to the Game Studio and the Platform involved.
You won't need to worry about the situation affecting you negatively as this is not going to impact your Campaign Completion Rate (CCR).