Circle of dreams druid, Halo fountain, Ghostly prison
My opponent had ghostly prison in play. During combat I had halo fountain (allows to untap a tapped creature to make a token), and a circle of dreams druid (tapping it created mana equal to the number of creatures). The combat order would not allow the halo fountain to appear as a usable ability.
My assumption is that the requirement to pay the mana superseded any other abilities that do not create mana. Luckily it did not cost me the game, but that is a major set back in the game. I have a log saved that I will attach but I dont know if it will be useful. Thank you for reading.