What should I check when an invocation seems to do nothing?

I would separate the two questions: whether you perceived a presence during the ritual, and whether the request led to an observable outcome later. Write down what you asked for and what you expected to notice, then review it after a set period. That gives you something more concrete to assess than trying to force a visual experience.

I would also check practical details like fatigue, lighting, distractions, and whether the group had agreed on what counted as seeing something. None of that proves or disproves a spiritual explanation, but it can help clarify what happened. Repeating the invocations more times is not automatically a fix.

Not seeing an image does not necessarily mean you performed the ritual incorrectly. People can have different expectations and ways of interpreting an experience, especially in a group. I would avoid treating everyone else's report as a standard you have to match.

A seer could be an option if that fits your practice, but agree in advance on their role and keep your own notes separate from their interpretation. If the main goal is a practical result, decide how you will evaluate that without relying only on a manifestation in the triangle.

My practical suggestion would be to pause before adding more steps or making the ritual more intense. Review your notes, make one change at a time if you choose to try again, and keep the request specific enough that you can tell whether anything changed. If the practice is causing stress or disrupting sleep, take a break.