A link becomes "outdated" in InDesign when a linked file is changed (e.g. an image edited, a PDF re-exported, etc.).

When this occurs, you can manually update the link from within the 'Info' panel of the one2edit™ Master Document Editor, as shown above (just click on the yellow triangle).

However, there is also a function to automatically update any outdated links as soon as the document is opened in one2edit.

Checking the 'Auto-update outdated images' box will ensure that any links that become outdated are automatically updated the next time the Master Document Editor is opened.

The option is found under the 'Settings > Client Workspace Settings' menu option.

NOTE:
This functionality will not help with missing links. It can only update an existing link, not choose a replacement link when the original one disappears.