First step to diagnosing the problem would be to run the permissions analyzer to verify the permissions (known to XF) are correct. Past that, you'll want to disable add-ons to verify if the problem persists without them.
Other than that, you'll need to provide details to investigate and test further. You can submit a support ticket with them and I'll look into it.
No, I tested members and admin accounts, their permissions analyzer all say YES but when I test my and their accounts, there's no option to vote. I tried editing the poll to open and close it, also did nothing. Just in case I'm too tired, here is what I see (answers removed). I see no way to vote.