Hello,
Across our company, people using the New Outlook for Windows are suffering the same issue with attachments not opening, previewing or allowing us to save, specifically .pdf file formats.
I've tried running an online Office 365 repair tool, I've also changed the default program for .pdfs from Adobe Reader to Edge on a hunch it was an issue with that. We're up to date on all Windows updates, and switching back to the Old Outlook works as normal.
The same issue occurs when trying to view the file with Outlook Online too.
Is there reported problems with this or a fix I can test/apply to a group please?