Error: extension subType <SESSIONEXTENSION subtype> for extension type <SESSIONEXTENSION type> is invalid for element <SESSIONEXTENSION name>.
In the XML file, you specified an invalid SUBTYPE attribute for the SESSIONEXTENSION element with the specified TYPE attribute. The SUBTYPE attribute must be compatible with the TYPE attribute.
Edit the XML file, and specify a valid SUBTYPE. Or, export the object again and then import it.