I am using Neo4j 3.5.18 version and upgrading from NEO 2.1.8. I exported the data via export command that generated graphml file. Then I went to NEO browser and used APOC import graphml command to import the file. Everything works fine till now.
I also have a java plugin (unmanaged extension) in $NEO_home/plugins folder. As soon as I enable this extension in neo.conf file my apoc import command stops working giving this error:
Failed to invoke procedure
apoc.import.graphml: Caused by: java.lang.ClassCastException: org.neo4j.helpers.collection.Iterators$EmptyResourceIterator cannot be cast to java.lang.Iterable