Co-authors not displaying

This is a follow-up to a previous support thread with @pokeyjoey.

This thread is specifically for our site since the Publishpress support team indicated the issues may have been different between the sites.

We tested a pre-release version from the support team (https://app.box.com/s/rscp6lvhwu32tdfx5olxkskp5ycxj1ph) on both a test site and a staging site.

On the test site, we were able to add co-authors.

However, on the staging site, we were not able to do that. The key issues remained:
1) It is only possible to add an author that is mapped to a WordPress user (it is not possible to add a Publishpress author as a single author). If I add 2 PublishPress authors (not mapped to a WP user), the post reverts back to displaying the default WP user as the single author.
2) It is not possible to add co-authors (only 1 author will display as long as it is a WordPress user as well).

We do have version Version 3.14.6 on the production site.

Let me know what you think!

The page I need help with: [log in to see the link]