If you have received a reminder email but you know that you have already completed your survey, you should check to see if you completed the survey using your own unique link or password rather than someone else's, or if you pressed the submit button at the end of the survey.
Find the original email provided to you by Survey Solutions (not one that was forwarded to you by someone else), and attempt to click your link or log-in using your password. If you receive a message saying that you have already completed the survey, you can disregard the reminder email saying that you have not yet completed your survey.
If you are able to access your survey without getting an already-completed message, it means that you did not take the survey using your own credentials, or you did not hit the submit button on your survey. If this is the case, please complete the survey with your own unique credentials.