P6 Export XML, Import into Unifier Schedule Sheet

I'm trying to export a P6 schedule and import it into a Unifier Schedule Sheet. I believe that I can export a P6 schedule in XML format and then use the "Import from External Source" option to import into Unifier. I've created a default data mapping (see below). However when I try to import, the file uploads but the schedule is never imported. I'm just trying to import activites, no WBS, resources or dependencies.

Has someone been able to do this successfully and if so, can you share the steps that you took?

We are on Unifier 10.1.7 and P6 8.2

Thanks