Login to Microsoft SQL Server Error: 18456

If you're trying to connect using "SQL Server Authentication" then you may want to modify your server authentication:

Within the Microsoft SQL Server Management Studio in the object explorer:

1. Right click on the server and click Properties

2. Go to the Security page

3. Under Server authentication choose the SQL Server and Windows Authentication mode radio button

4. Click OK

5. Restart SQL Services

Check out this blog article from the data platform team.

http://blogs.msdn.com/b/sql_protocols/archive/2006/02/21/536201.aspx

You really need to look at the state part of the error message to find the root cause of the issue.

2, 5 = Invalid userid
6 = Attempt to use a Windows login name with SQL Authentication
7 = Login disabled and password mismatch
8 = Password mismatch
9 = Invalid password
11, 12 = Valid login but server access failure
13 = SQL Server service paused
18 = Change password required

Afterwards, Google how to fix the issue.

Before opening, right-click and choose 'Run as Administrator'. This solved the problem for me.

I have faced this issue.

Please look at the attached image,

Step 1: Go to server property

Step 2: Go to Security

Step 3: Change server authentication as SQL server and WindowsAuthenication mode

and restart your Sql server.