If you're unable to log in to CostOS as an administrator (for example, you've lost the administrator password).
Login to SQL Server and run the follow query on application master database.
UPDATE [{MASTER_DATABASE_NAME}].[dbo].[PRINCIPALS] SET AUTHTYPE='LOCAL',ENBL=1,HASHKEY='5C3B68-43-501A-4B-73',PASSWORD='5C3B68-43-501A-4B-73' WHERE PRINCIPALID='{RESET_USER_USERNAME}'
Replace values {MASTER_DATABASE_NAME} with application master database name and {RESET_USER_USERNAME} with the username of the user that you want to reset.
The new password is 'admin'