The error "Database connection verification was not successful" when trying to activate the Manager for SQL Server in Dollar Universe superior to 6.2.x The error that appears is "login failed for user 'domain\username'"
The Dollar Universe Manager for SQL Server only support Internal Microsoft SQL Server Users.
Dollar Universe 6 on Windows
You need to use a SQL Server Internal User to use the Manager for SQL Server. Extract from the documentation:
Login/Password: Provide a valid SQL Server account and password.
To connect to the SQL Server instance, the Manager uses an SQL existing account (user and password). The SQL login must be associated with the public and sysadmin roles. The sysadmin role is required to be able to manage SQL jobs.
The Manager system account does not have an impact on the connection.