I think you've got 3 choices here:
1. Confirm you are inputting the correctly spelled password required for access. You need to confirm also that WPA2 is indeed the correct encryption ... could it be WPA or WEP instead?
2. Access your router (hardwire) and reconfigure your wireless settings, including resetting your WPA2 password.
3. If you are unable to access your router due to router password, then you may be forced to reset your router back to factory defaults and reconfigure your wireless settings.