It may be that you have the same IP as someone else who voted. The poll checks for IP address to prevent people from voting more than once...but I would think that if you have the same IP as someone (or if someone else used your computer and voted) it would then not let you vote.
Since you don't have your "own" IP address, it will probably let you vote the next time your IP changes.
We're going to be changing the poll shortly as well, anyway 🙂