When working with Data Connection Libraries in InfoPath Designer, sometimes the recently added connections will not appear! specifically when choosing the option “Search for connections on a Microsoft SharePoint Server”, and then selecting any previously used library inside the form, looks like the InfoPath Designer is using a cached version of the selected data connection library!
To solve this issue you need to clear the cache of InfoPath Designer using the following ways:
1- Close the InfoPath Designer->Start->Run-> and run the following command: InfoPath /cache clearall
Running InfoPath Designer by passing these arguments will automatically clear all the InfoPath Cache.
2-All the cached files of InfoPath Designer is stored in the following path: C:\Documents and Settings\[User]\Local Settings\Application Data\Microsoft\InfoPath\FormCache2
To access this folder: Start->Run->%LOCALAPPDATA%\Microsoft\InfoPath.
You will see the following folders:
You just need to delete the contents of the FormCache3 Folder, the other folders content will be deleted automatically by the InfoPath Client Designer.