In fact, I don't know why. In any case, many downloads from the mailbox can't be opened. But you can try to open the ppt, click the file menu, click "Options" - "Trust Center", click "Trust Center Settings" in the lower right corner of the trust center, and click the "Protected View" option on the left side of the "Trust Center" interface,In the right window, uncheck "Enable Protected View for Files from the Internet", confirm to save, and then open the file to try.I can change it in this way.
