Respondents get the message “survey already completed”

This occurs when respondents fall within the session of a previous respondent. It’s often because the survey has been opened and the URL copied from the browser and shared (e.g. via Twitter, Facebook, etc.) This URL then contains information about the previous person. Therefore, the survey link provided in the survey menu is the only one that should ever be posted. If you wish to encourage your respondents to share your survey, post the shareable link on the first and/or last page of the survey. 

Multiple respondents using the same PC? If this is the case, you should definitely disable cookies in “Project settings” → “Login options.” A new session will then begin whenever the browser is closed after completion of the survey and the next survey is launched in a new window.

If the surveys are not completed from the same PC, but from the same network (e.g. a college network), this issue may be caused by the use of proxies. In this case, we recommend accessing the survey with https:// rather than http://. This activates SSL encryption and solves the problem in some cases.