Can't configure mart server: Data access error. Verify your credentials. OR The connection to the server ., port 1433 has failed.

Problem:

I am trying to configure my mart server. I am typing the correct SQL server server name and database user password but that keeps giving the error,
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Mart Configuration
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Data access error. Verify your credentials.
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OK
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If I switch the server name to the shorthand which is a period (.) then the error changes to be,
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Mart Configuration
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Data access error. The connection to the server ., port 1433 has failed. Verify the server name and port number.
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OK
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But that does not make sense because I have tested port 1433 and I know it to be open on that machine.

When I check the MartServerUpgrade file that is stored in the directory C:\Users\username\AppData\Local\CA\ERwin Mart Server\logs I get errors similar to the above:

case 1:

Oct 18, 2017 1:53:16 PM com.erwin.mmappserver.start.MartUpgradeProcessor main
SEVERE: null
org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Login failed for user 'sa'.)

Case 2:

Oct 19, 2017 9:56:01 AM com.erwin.mmappserver.start.MartUpgradeProcessor main
SEVERE: null
org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (The TCP/IP connection to the host ., port 1433 has failed. Error: "null. Verify the connection properties, check that an instance of SQL Server is running on the host and accepting TCP/IP connections at the port, and that no firewall is blocking TCP connections to the port.".)

How do I resolve this problem?

Solution: 

Your SQL server is probably set up only for Windows Authenticated access.  Please change that instead to be SQL server and Windows Authenticated access.

Launch SQL Server Management Studio

Go into Properties on the Server

Choose Security

Make sure the below item is selected 

Restart the SQL Server and that will resolve the problem.

NOTE:  If the mart configure window is still not working, try logging into SQL Server management Studio and check if the user account has been disabled somehow:

(a)Expand the SQL Server

(c) Expand Security node

(d) Select the Particular Login (User)

(e) Press right button and select properties of the login

(f) Go to the Status table and Enable the User

 Then try to login