If you don't have a BES, you are in the wrong section of this forum. The BES Admin corner is only for questions related to BES.

I guess you are probably connected via IMAP (through BIS) and calendar sync is not possible. Go to your calendar > Options > Accounts. See if you have an option "Wireless Synchronization" and make sure it is ticked. If you don't see that option, calendar sync is not possible.