Login fails after password reset or new user creation despite updating password in database

I am encountering a critical issue where I cannot connect to my SQL Server instance using the sa user, even after resetting the password via SQL Server Management Studio and after creating new users. The error message received is:

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Cannot connect to Mubashir.

Login failed for user 'sa'. (Microsoft SQL Server, Error: 18456)
Details:

The problem occurs when attempting to log in to SQL Server using the sa account.

Password reset attempts for the sa user have been performed both through the application and directly via SQL Server Management Studio.

New users have also been created with known passwords, but login attempts for those users fail as well.

The error corresponds to SQL Server error 18456, indicating login failure due to invalid credentials or possible permission issues.

The issue persists even after verifying that SQL Server services are running and that the login names exist.

No additional errors or messages are shown except the login failure notification.

I have reviewed Microsoft documentation for error 18456 but have not resolved the issue.

What I have tried so far:

Resetting sa password through SQL Server Management Studio.

Creating new SQL Server users with proper roles and passwords.

Checking SQL Server authentication mode (confirmed it is set to mixed mode).

Restarting SQL Server service.

Ensuring no network or firewall blocks.
@microsoft/mssql-server, @mattn, @brettcannon, @gregturn, @SqlChicken, @bradleyh

No repository file, test, or entry point is identified; start by determining whether this SQL Server login report applies to a sample in the repository rather than to local server configuration. Done would require a reproducible repository-specific failure and a named sample or test to change.