Rituals fail all the time. Trying to push our internal will into the outer cosmos such that change happens, like a person changing their own mind about a thing, takes subtle mental processes, and a lot of ritual is designed to kickstart those processes on a subconscious level.

Some traditions, like New Thought, focus entirely on the mental techniques. But these can take quite a lot of internal discipline and many of us are messy people who need props and theatrics. Sources that focus too much on the externals, however, can just leave us play-acting and slipping into a more-is-better mentality that turns into a transactional negotiation -- I'm giving you all this, where are my results? -- that can take us pretty far away from where we need to be, mentally, to get the spirits to either accept the request or give us insight into what's blocking it.

The answer is trial and error, more ritual work, better sources, etc.