importing task and events/ association with contacts

importing task and events/ association with contacts

I'm trying to import some tasks and events to finalise the conversion to Zoho Professional. However, the association with my contacts is not imported. In the CSV file a field has been made with the exact (mandatory) Contact Name. This is the field with which I associate the event. However, after finalising the import (with no errors reported) the association is not made.
 
Any idea what I'm doing wrong?
 
Thanks for your support