Just wondering if anyone else has run into this problem.

Playing through Final Fantasy 2: Soul of Rebirth on Android and I just defeated the Ultima Weapon to obtain the Ultima spell. The only problem is the game will not allow me to equip the spell to any of my characters. All of them have the room to equip the spell. I want to give it to Scott since he has the best balance of my party in terms of higher level spells and weapons/equipment but even if I try to give the spell to Minwu, Josef or Ricard I get that dreaded error sound and nothing happens. What gives?