I recently changed handsets to a Samsung Galaxy S4 and started to restore my Whatsapp message but the restore was interrupted and has not continued the backup. How do I complete the Whatsapp backup restore?
You can contact WhatsApp support and explain your issue. They'll surely help you.
However, it might have been because of interrupted data connection, or the thread might have been unexpectedly stopped.
You can uninstall and reinstall the app. It should then work properly.