SQL Server database 18456 error how to solve?

1. Enter the database Manager in Windows Authentication mode.

2. Right-click the SA and select Properties:

In the General tab, re-fill in the Password and confirm the password (changed to a good note). Remove the mandatory password policy.

3. Click status tab: Tick Grant and enable. And then determine

4. Right-click the instance name (the part that draws the red line) and select Properties.

5, point Security, confirm that SQL SERVER and Windows Authentication mode are selected.

6. Restart the SQL Server service (important).

SQL Server database 18456 error how to solve?