Be careful in your expectations regarding prayers published with phrases such as “never known to fail” and “the prayer must be published.” In my opinion, such phrases should never be written on prayer cards, since they can be very misleading, and the Church does not publish prayers that way. (These things have usually been printed by well-meaning but mistaken individuals.)
We can’t be superstitious about such things, expecting that we will receive exactly what we ask for, exactly how and when we want. Religion is not a vending machine where you insert coins (prayers) and get exactly what you ask for!
That is not to say that Mary and Our Lord have not heard your prayers. They certainly do hear your prayers, and God will answer you in the way He sees best and in His own perfect timing.
What you need to do is to trust God that He knows what is best for you.
Think of “never known to fail” in this way: God in His merciful love can bring good out of any broken situation, in mysterious and unexpected ways.
Offer the suffering you are experiencing for the salvation of souls, including yours and the other person involved in this broken friendship. And try to learn whatever lesson God may have in mind for you in this situation.
God bless you!