The error is: "Photoshop.com services are currently unavailable. Please try again later or check your network connections. Error 400."
When you try to log in to Photoshop.com services from the Photoshop Elements Welcome Screen, you receive an error message associated with previously available functionality.
If you are on the Welcome screen, it's unnecessary to log in to Photoshop.com to use the Editor or Organizer. Click OK, and choose to use either the Editor or Organizer without signing in.
Alternatively, you can bypass the Welcome screen by opening the application files directly.
Elements 10, 9, 8, and 7 Organizer include a Backup/Synchronization feature. It automatically uploads and downloads the images in your catalog to and from Photoshop.com's Sharing and Storage servers.
On July 15 2013, these Sharing and Storage servers were shut down and the services Photoshop.com provided were discontinued.
For more information about this change, see http://www.photoshop.com/misc/membership-faq