The login was mapped to the database as the dbo, which is wrong. It happened because this account actually created a database during the installation.
The login already has an account under a different user name. (Microsoft SQL Server, Error: 15063)
To resolve this
Please run the script against your database:
Then just re-map your login DomainName\Sharepoint-Services to the database (double click on the login->User Mapping->check your DB->check Datareader/Datawriter->Ok).