This happens when someone on the same network (office network / computer, home) has already voted.
EXAMPLE: Let’s say you are in an office environment, and someone votes on their work computer. If you then tried to vote on a different machine, since someone from your office has already voted, you cannot vote from your office.
If you would still like to vote, feel free to vote via your mobile phone’s web browser, or at home.
We apologize for the inconvenience.