This error indicates the Master Encryption key is missing or incorrect. The encryption key will need to be reset

Note: we strongly recommend you attempt to locate the previous Master Encryption key prior to doing a reset. If you are unable to locate the previous key, a new key will need to be created. Creating a new key erases all passwords within the NetCommunity website. This includes all passwords saved under Administration>Sites & Settings and all passwords under Users & Security>Users. Every password for the Web Services will need to be reentered and every user will need to reset their password.