Umberto, stop worrying about what people might be thinking about you and just do what you feel is best.
These kinds of thoughts, second-guessing your responses, only serve to undermine your confidence.
Based on what you wrote, it is unlikely that clients are “testing” your knowledge.
You’ve forgotten more about architecture than they will ever know.
What is more likely, is that they didn’t move ahead because they don’t understand exactly what you are giving them, or how valuable it is.
Keep on moving forward and after every setback (and success) ask yourself: What can I learn from this?
So what can you learn from this? – Enoch