accessing F5,owa2010 can not change expired password

Password changes are done via Exchange Control Panel(ECP) - which is a different site/App on IIS from OWA. Can you successfully get into ECP(https://mail.yourcompany.com/ecp)? If not, what exactly is the behavior? If you configured SSL offload, you need to disable SSL required on that site in IIS as well in order for it to work with F5...