Unable to display images–uploaded files appear as classic blue question marks

I’ve been blogging since March 2014 and haven’t had any major issues. Recently I discovered that file images uploaded from my “Media library” do not appear on the page. Instead they are replaced by the blue question marks. When I upload images via direct URL links however, they appear. I’ve tried resetting my cache and cookies. I’m not really sure where to go from here. Here is the ‘index case’ blog page:

https://www.thethinkersgarden.com/2014/08/23/tullia-d-aragona/

thanks in advance for all your help