So I am able to send a character expression to Zbrush from CC4 using the Expression Editor's "GoZ (Expressions)" button. 
However once it is in Zbrush it is not being allowed to come back into CC4. Instead when I try to send it back I get this text back in return:



I thought it was something I was doing so I sent it through again and then clicked GoZ again without making changes to the mesh and got the same message.
Does anyone know how to resolve this or what is going on?

Thank you in advanced.