By default, the SQL “sa” user account is disable and prevented from login purposes. You can refer to this article, How to Check if “sa” User in SQL Server is Renamed / Disabled article to figure out status of “sa” account in your SQL server.
SELECT name, sid, is_disabled FROM sys.server_principals WHERE principal_id = 1;
Alternatively, you can obtain the status of “sa” account as per below screenshot. From SQL Studio > Security > Logins. (red arrow icon)
Solution
Launch the SQL Management Studio, right click on the server instance and select Properties.
Under Security page, select SQL Server and Windows Authentication mode. Click on OK.
Restart the SQL service.
Next, login back to the SQL Management Studio, open the Logins page (under Security) and select Properties.
Go to Status page, select Enabled for Login and Grant for Permission to connect to database engine.
Enter the password for the “sa” account. Click OK.
It’s done. You should be able to login with “sa” user account now.
Alternatively, you can use below command line to maintain the password for “sa” and enable it.
alter login [sa] with password=N'NEW-PASSWORD'
alter login [sa] enable
