Revert to using local account for SQL Server services

We have changed the login/startup account of our SQL Server service, to use a domain service account. However, we are experiencing issues with this account, and need to revert back to using the local NT Service\MSSQL$[namedinstance] account for now. Is there a way of doing this? When prompted for the password in SQL Server Configuration Manager, what does one enter? We never set a password for this previously, but it appears to require one. > The account name is invalid or does not exist, or the password is invalid for the account name specified. [0x80070421]