The 84-player match has disappeared since the new Empires Fall. I don't know the exact reason for the missing 84 player match, but I can guess; it is likely that the developers removed this match in order to concentrate the players on the new map. So that they actively play on it, notice errors and shortcomings, and then report it to the developers. If so, then the decision is quite wise.
Now the match for 84 players is not available and no one can enter it. However, for several days in a row, I am asked to enter an 84-player match for gold. Is this a bug? Is this a defect? I don’t know, but it’s unlikely that anyone else would have played in that match. Hence it follows that the meaning of this tablet disappears. I'll leave it to the developers. They know better whether this is a mistake or a temporary measure.