Sa account creating using single user mode

Question

This is our production server. I set up the server in single-user mode and attempted to create an SA account using an SQL query in CMD, as mentioned in the image above. However, I am facing the mentioned issue. On the test server, I was able to create the SA account using the same SQL command. I am using mentioned sql query to create sq account on test server CREATE LOGIN newsa WITH PASSWORD = '12345678';

ALTER SERVER ROLE sysadmin ADD MEMBER newsa;

GO