First make sure the ballot is active.  When you first enter the ballot configuration program, you should be confronted with a popup window indicating the Ballot Voting Period Has Started.  If the ballot is indeed active, carefully check the eligibility rules specified for the election to make sure the account you are checking is eligible to vote according to those rules.  Pay special attention to the Membership Designations Excluded.  It is a common mistake to accidentally include the wrong Membership Designation(s) in the exclusion list, thereby keeping members that should be eligible to vote from seeing the ballot in online banking.