To add to the excellent reply by Nuralshamal,
often things don't work for very simple and straightforward reasons.
Prayer it's very mechanical: you give energy, you get bleesings. Sometimes you need to put candles and materia. Sometimes you just need more time. Sometimes you need some link to the target.
There is an excellent book about this called "The Elements of Spellcrafting: 21 Keys to Successful Sorcery". Don't get scared by the word sorcery, it's intended very differently from common usage. The stuff there relates a lot to prayer!
