It is impossible for LiveProject to perform any meaningful action on an orphan suggestion because the task/resource it belongs to no longer exists.
In this window, the Manager can reject all or just some of the orphans. As long as there is at least one remaining, the Orphan Button will show up in the Review Project Suggestions window. You can select multiple rows by holding down the CTRL or SHIFT keys while clicking on the rows.
To get more information on an Orphan, contact the sender of the suggestion.
To avoid Orphans, be sure to publish regularly so participants do not work on old versions of the project file.