спецом проверил, у меня всё заработало
USE [master]
GO
CREATE LOGIN [bla] WITH PASSWORD=N'bla', DEFAULT_DATABASE=[master], CHECK_EXPIRATION=OFF, CHECK_POLICY=OFF
GO
—connect to master with bla user creds
USE [master]
GO
ALTER LOGIN [bla] WITH PASSWORD=N'bla1' OLD_PASSWORD=N'bla'
GO