If nothing was unclear or difficult, say so. Skip questions about steps you did not experience; use not applicable where appropriate.

What experience does this invitation ask you to have had?
Which part of the invitation explains why you were contacted?
What would help you decide whether to start the questionnaire?
Which instruction is unclear if you begin but cannot finish?

Author notes / illustrative keys where applicable:
1. Check whether the stated experience matches the intended invitation cohort.
2. Find ambiguity in eligibility rather than interpreting nonparticipation as disinterest.
3. Separate unclear purpose from missing access or time.
4. Clarify the partial-completion route without pressuring people to finish.