Cannot find the declaration of element 'processDefinition'

When attempting to install a new app in my Bonita server from a .bar file I created from a proc file in Bonita BPM, I keep receiving the following error message:

org.bonitasoft.engine.bpm.bar.InvalidBusinessArchiveFormatException: javax.xml.bind.ValidationException

  • with linked exception:
    [org.xml.sax.SAXParseException: cvc-elt.1: Cannot find the declaration of element ‘processDefinition’.]

But I have no idea what this processDefinition could be related to.

Which version do you use? What exactly did you do to “create a .bar file”, did you build/export it from the Studio?

I am using 6.3.1 and I used: Server → Build.

Edit: Actually it looks like the server is running on 6.2.1 while the developer is 6.3.1