I haven't voted, as that seems to be a ticket to "Solve it then, smart mouth!".

It does
seem solvable, though. I'm assuming someone more patient than myself being involved.
I don't think a campaign ending with an unsolved riddle is necessarily worse than one that ends with everyone dead after failing in combat; depends on the overall nature of the campaign, I would think.
Below is a stab. It may not be right, but it has a certain easy logic. Without someone having the correct answer, and saying one is either right or wrong, I am not sure there is any resolution. I think this one is right, myself, and there is nothing that I can
see is wrong with it, since the puzzle has no context.
C C C A A A A A A C C T T T T
C C C A A A A A A C C T T T T
C C C A A A A A C C C T T T T
C C C C A A A A C C T T T T C
C C C C A A A C C C T T T C C
C C C C A A C C C C T T T C C
C C C C A A C C C T T T C C C
A C C C A A C C C T T T C T C
A C C C T T T C C T T A A T C
A A T T T T C C C A A A A T C
A A A T T T C C C A A A A T C
A A A T T T C C A A A A A T T
A A A A T T T T T T T T T T T
A A A T T T T T T T T T T T T
A A A T T T T T T T T T T T T