Downloaded files won't open

Same here, but NONE of my downloaded files, from any source--even e-mail attachments from people I know & trust--or any format (PDF, JPEG, etc.) will now open on my 2017 MacBook Pro. I can download the attachment, and it shows up in the "fanned" array of downloads when I click on the Downloads icon in my dock--but when I click or double-click the item's icon the array collapses--it's like it's playing peek-a-boo. I bet it has something to do with those new automatic security updates. I was able to open the attachment on an iPad and print wirelessly, but this is driving me nuts. The document in question is a PDF of a contract which I must return and sign, with a deadline.

I found the culprit is the app OneDrive -embedded in MS 365. It started taking ownership of my Excel and Word documents and has moved on to entire folders and more -permissions and all. It's spreading & geting worse. There are files I can't open or save, or even close unless I save to OneDrive, I get alerts I don't have permissions to change, move, delete or or add files to folders I created on my iMac & even external drives. And everywhere I look on my computer I see peculiar files with "onedrive" somewhere in their name.

I've tried to get rid of it but it keeps coming back. I can't just trash it because it keeps files hidden that I need and can't find. Online I found articles explaining the 1st step: stop the OneDrive "sync." Then I'll try to get all my files back, reclaim permissions to my drives and folders, delete OneDrive and all the helper apps and folders, and finally delete MS 365 and end my subscription.

Eventually I'll either switch to Pages & Numbers (which I don't like, but still...) or will buy individual Excel and Word programs if they still exist.

This is what I've found. don't know if it helps anyone here.

This sounds like a Microsoft issue to me. Have you talked to them?