Blessings like "Cure Disease" have the condition: may only attemp this blessing once per disease.

It is clear that a failed attempt still counts, since a succesful attempt will cure the condition/disease/insanity.

But how does this limitation work?

Can a second priest cast the same blessing if the first priest failed?

Can the same priest cast the same blessing after one day?

Without looking too closely to the rules, i would use an approach like "a try per day", maybe if you want to be more severe a try every "severity rating" days.

A different Priest using the same Blessing would not help more if already succeeded/failed once.

The same Priest can use the same Blessing the next day (or try period), praying this time he is more successfull.