Mac OS local accounts or mobile accounts are able to initiate encryption on Mac OS X Mountain Lion or later. Other Mac OS user account types will be unable to initiate encryption.
If a Mac OS account other than a local account or mobile account attempts to initiate encryption, the following notification appears:
The following task shows how to create a mobile account for your Mac OS account to bypass this issue.
The System Preferences window appears.
Your mobile account has been created. You may now use this mobile account to initate encryption.