Unable to upload anything

I am unable to upload anything, no file I've created since 1/10 is displayed in the file list. And when I try to drag over a file that is there, I get a barred circle sign over where I should drag it (sorry don't know technical terms). Have been using Smart for a few years and this is the first time things won't save. I use FrontPage. I'm desperate to update my web page, can anyone help?