Error Migrating from vmware 5.0 to 6.0

Hello,
This is mysituation.
I have4 serverswithESXi5.0managedbyvCenter5.5VM.
I receiveda newserver is notcompatiblewithESXi5.0 and5.5.
I installedESXi6.0 andvCenter6.0on itonVM.
I importedthe newDatacenter4Host5.0.
The problemisthat I can notmigrate/clonevmfrom hosts5.0to6.0new host.
The erroris the following:
"The operationis not supportedon theobject."

What should I do?
Tell mewhereI'm wronglike I was ababybecause I'm notan expertin this area.

Thank you.

Nicolò