I have seen this problem started suddenly. I regularly upload shapefiles that I have compressed into a zipfile, by going to "Add item" from the content page. I fill in the title, tags, etc. but when I press "upload"/"ok", nothing happens.
The nature of the shapefiles that I try to upload hasn't changed, and it's always worked fine before.
However I can add these shapefiles from my computer directly from the map viewer in ArcGIS Online, although they are not reflected in the items in "content".
Has anyone experienced a similar issue in the last month (February 2019) or at all? Any advice?
Thank you.