In a personalized survey, study participants repeatedly received the following – false – message from the system when trying to access the survey: “Many thanks for your interest but the questionnaire has already been completed.”
However, this message appeared the first time that they tried to click on their personal survey link (password link copied from the system). Therefore, they could not access the survey which is critical for our response rates. Sometimes, but not reliably, resetting their data (in “participant administration”) worked. Sometimes copying the link into the browser rather than clicking on it worked. But none of these solutions worked reliably.
How could we avoid this? Grateful for any explanations/ suggestions.