The curia doesn't work, if the Papal State doesn't exist. Normally, when the Papal State is destroyed, which it is due to your converted CK2 save, another catholic theocracy becomes the Papal State. If none of those exist as well, the Papal State is gone forever and the curia is removed.
I presume, due to your save game conversion the trigger to remove the curia didn't fire or the trigger to move the papal state to another theocracy, if it exists, didn't fire. So whoever is curia controller now will remain so for all eternity. You may possibly destroy the curia, when you conquer whoever is curia controller now, but I'm not sure.