Whenever I try load load a pptx file Aspose throws an exception saying "The file is ZIP archive. It can be Microsoft PowerPoint 2007 PPTX presentation."
Thanks for your interest in Aspose.Slides.
I have observed the issue shared by you and it seems that you are trying to access the PPTX using Presentation class. You need to access the presentation using PresentationEx class. Please import Aspose.Slides.Pptx namespace in your project. Please visit this link for your kind reference.