Convert to a video is certainly an option, that’s something we generally suggest.
That being said, the registry changes here https://xibo.org.uk/manual/en/media_module_powerpoint.html
and here PowerPoint media items show a "Navigation Cancelled" error when running on the Windows Player / PowerPoint brings up an Open Dialog
Have you added all of that already?
It should get rid of those pop ups and PowerPoint should be played fine on the Xibo for Windows player - assuming full PowerPoint is installed and that it is enabled in the display profile assigned to your player, but I think you’ve already done that.