Powerpoint presentations cannot be automatically updated/uploaded once added to your Layout.
There are 2 methods for adding a presentation to your layout, I have included a link below to the Documentation that explains how to do this. The first option of exporting the presentation as a video is recommended, as this does not require a copy of Powerpoint to be installed on all players that will be using that layout, which is much more cost effective.
If you would like to update the presentation in your layout, you will need to modify the presentation, export as a video or prepare a new PPT file, then add this new version to the layout, remembering to remove the old version.
Depending on how often you will be updating the layout, you may wish to create a script for our API, to automate the file upload and add it to the Layout. I have included links to our introduction and manual for our API and a link to the API documentation:
https://xibo.org.uk/manual/fr/cms_api.html
https://xibo.org.uk/manual/api/#/library
Many Thanks.