You can manually update an item when auto update fails.
If you have an item checked out and someone else creates a new version of the auto-update linked file, the system cannot automatically create a new version of the item until you check it in. You can manually update your local copy of the item to link to the new file version.
You can only update the link if you have the item checked out. If another user has the item checked out, you must wait for the item to be checked in, then you can get the latest version of the item.
Item Explorer displays items with stale auto-update links with 
(the item icon with a green refresh overlay) and red text.
To update an item when auto update fails: