Hi @praveengeorgeix 

It is possible that the responders has mistakenly opened the link in two tabs.

Also it is possible that responders opens the survey but never completes it which can lead to session expire.

Its a age old question without answer.

Context:

• I deleted all responses from my database.
• Link is anonymous
• Settings as below

 

Do you know why Im getting this error?

There is one possibility that you have deleted the distribution of survey and after that you are accessing the live link.

Good morning from a sunny Sweden! 
I would say that it’s more a question of what setting you have for the below: 
 

Because Qualtrics capture a lot of your computers identifiers which makes it see that you’ve taken the survey before. I usually turn this Off during the testing-phase and then turn it back on when I’m ready to go live with the survey. 

All the best

-Mattias