I cannot attached a document from my desktop to my outlook email

I cannot attached a document from my desktop to my outlook email. It shows the document attached but with 0 KB so basically no size as if its not there. And then moments later it disappears. It doesn't matter if its Word, PDF, txt, xls, etc.  Could it be a CLOUD thing not downloading my doc so that I can attach it? Seems odd because I can open the file no problem, so why can't i attach it? This JUST started and i haven't changed any settings so again, very strange. thank you for your help!