The stronger a light shines the darker are the shadows around it.
I put your query to Tony Sir. He said that both power points and .jpg files should work as attachments, but he suggests to avoid a large powerpoint file since it will overload the site's servers. Maybe you were trying to upload a huge file? Unless the power point can really add value and is unavoidable, you could upload a small PPT file. It would be better, though, to upload .jpg files.
I also think it would be possible to upload PPF file on YouTube and then share the YouTube video via embed feature, placing that in your article. There, too, it could be a short video and not too heavy or over-lengthy.
When you make a commitment, you create hope. When you keep a commitment you create trust! ~ John C. Maxwell