If you recently changed your certificate for your Exchange server this might result in OWA and ECP not working properly. The problem is that Exchange doesn’t update the certificate in IIS “Exchange Back End” site. So you have to do this manually.
- Open IIS
- Navigate to “Exchange Back End” site
- Open bindings and edit the HTTPS binding
- Make sure that the binding is configured with the new certificate
- Restart IIS
IT&C Blog 