I set cookie to prevent repeated participation and worked well at first.
So I deactivated the survey and started it again. However, it is now showing some users that they already completed it.
I thought that when I deactivated, it would start all over again.
No, not really. Because the cookie is still set. You can't really undo the cookie that easily.
I am not 100% sure what is stored in the cookie, but I assume that the survey id is stored (so that people can take part in various surveys).
If you copy the survey, this basically should create a new one and they respondents should be able to take part again.
Help us to help you!
Provide your LS version and where it is installed (own server, uni/employer, SaaS hosting, etc.).
Always provide a LSS file (not LSQ or LSG).
Note: I answer at this forum in my spare time, I'm not a LimeSurvey GmbH employee.