Odd one just before Christmas. PowerPoint would not load into the schedule when using the "add item" at the top of the screen but would still load if you added it via the Presentations library.

(The reason we do this is that we have a weekly PowerPoint, prepared by the Church Office, called "Notices". If we add via the presentations database we need to remember to delete last week's first otherwise we have two presentations with the same name!).

However, last Sunday, when we added the PowerPoint (via the presentations database) it was on the schedule but would not display. It moved to the Live area but clicking the first, or any, of the thumbnails gave no output either on the Live output preview or the screen.

As far as I know nothing has changed on our system since it was working fine, Win 10, Office 365. Current EW6.

While this won't address your not loading issue, it might help with the duplicate files with the same name. Add the date in the name of the file each week. We do that so we always know which one to load if someone forgets to delete the old one.