Collaborator insists on downloading .docx files in a review.

Hi

I have not used Collaborator for a while and am trying to start again.

I see we have version 13.4.

I am trying to start a review. As a test, i am saving my file both as a .docx and a .pdf.

I upload both my files to the review and I see them there.

When I open the .pdf, it shows me the file and allows me to comment - like I was expecting.

When I open the .docx, it insists on downloading the file to my pc and making me make the changes on the local copy - which defeats the purpose.

What am I doing wrong that I can't setup a review of a .docx so that I can make changes on the collaborator copy of the file?

Thanks in advance for any help.