Roll in another channel or try my method:
Try to roll for something else in the same cap as Zeta or ZZ, and the A rank will come out. It doesn't make sense but I always believe that fate will give us something the opposite of what we want. At least in SDGO it is fool proof for me. Don't do it in Dream Gacha or Custom cap though since you'll NEVER get it with this method.
"You are already dead."