Symptoms

The Sync fails and produces a log line that includes the following:

Unhandled Exception: Unhandled Exception: System.InvalidOperationException: There is an error in XML document (1, 418). ---> System.FormatException: Unrecognized Guid format.

Diagnosis 

There is an <IglooGroup> or <GroupID> in the <Groups> or <OneToOneGroups> in the ILST config file that does not have a valid group GUID in it.

Actions

• Confirm that all <IglooGroup> or <GroupID> fields have a GUID in them that matches an existing group GUID in your community. You can check your group GUIDs by following the steps outlined here