Vote button Missing in outlook 2010

I have one issue where user cannot see "Vote" button. Here is the details. User (reciepient) is using outlook 2010. The user receives email with Voting enabled from same exchange 2010 organization. The user does not see the "Vote" button in the Respond ribbon area. "Accept" and "Reject" button appear but they are greyed out. Message with "Vote by Clicking......." does appear. No "Vote" button though. I cannot replicate the issue in my test environment.