It's every ritualist's worst nightmare, and—if you stay in the field long enough—it will happen to you.
Your ritual bombed.
What do you do now, dear?
Well, the worst thing that you can do is to slink away shamefacedly with your tail between your legs.
The reason why this is the worst thing that you can do is that it breaks trust.
No. Instead you need to buck up, gird up your loins, and publicly confess.
“Well, that ritual bombed,” you need to say. “What I want to hear from you is what didn't work, why it didn't work, and how we can do it better next time.”