Why won't my pumice pieces work at Hades synthesis shop?

[sullivane70/Irishprincess]

I have two blue pumice pieces and i'd like to get the ark summon, but Hades doesn't seem to accept them. Am I missing something?

[Xengre]

Is it equipped by chance? Are you sure you have two Pumice Pieces? Do the other synthesis work at Hades or are they all broken possibly?Just in case, lastly, are you sure you didn't already make it and are mixing up a Pumice Piece and a Pumice? There are three pieces IIRC so you might have already forged Pumice and thus only actually have one pumice piece left and the other is a full pumice (if its not the equipped issue).