I've done some research and: "As of Patch 4.1, Players can complete the Main Scenario Quest The Ultimate Weapon to recieve one. Players can no longer obtain a Fantasia through Veteran Rewards."

That's why I only one.

Skip potion says that you will gain ALL the rewards from MSQ, should surely include fantasia potion. But I think if OP used before 4.1 and did not receive as a vet reward, then its gone.