Thanks for your quick reply. Upon checking on the XML that worked, one difference I noticed is that on the DBPort field I specified the port number (I used 1433). On the latest one I didn't put anything as the web UI specified that if we leave it blank it will use the default port 1433. I tested it again now specifying the port and it was successful connecting to the database.
<Database>
<DBServer>SP2013-SQL2014</DBServer>
<DBAlias DBPort="1433" DBInstance="SP2013-SQL2014\MYSSQLSERVER" Create="true" />
<DBPrefix>AutoSPInstaller</DBPrefix>
<ConfigDB>Config</ConfigDB>
</Database>