When attempting to copy an item, Sharegate displays the following error message:

Cannot map the lookup value '1' at the destination because it points to an ID field and there are no Unique Key properties.

Any error code ending with: -245

This error occurs when Sharegate is unable to convert a lookup value pointing to an ID field. To convert it, Sharegate tries to find the corresponding item at the destination using the Unique Key properties that have been set in the Property Mapping to match the source item and the destination item. If there are no Unique Key properties set, there is no way to find out which item at the destination matches the source item pointed at .

Make sure to set your key properties properly using the Map Properties screen. (See this article for help on setting the key properties)