If enough time has past and you feel the spell truly hasn't worked, we will do one more spell casting for you, free of charge. We will discuss why we think the spell didn't work, so that we can work around that for you. The minimum amount of time that needs to have passed is three months.
With energy work, there is never an absolute guarantee, no matter who is casting the spell. Sometimes a spell will fail because there is a Divine plan for you. If a spell goes against what your soul contract is, then no amount of spell energy is going to be able to change that. However, usually spells do work beautifully. It's quite rare that you would be guided to ask for a spell that goes against the Divine plan for you.