image disappears every night

My Omeka site (hosted at Omeka.net) is set up to load a Simple Page as a homepage. In it, I have a banner image. Every day I put the image into a simple page with the HTML. It shows up fine all day.

But the next day, it's gone. There's a box with a question mark inside it: http://poetryinthearchiveshuvcp.omeka.net/home.

The image is still available in OMEKA, but it won't load correctly in the simple page.

Is the image too big? Why does it show up temporarily and then disappear?
https://s3.amazonaws.com/omeka-net/23137/archive/files/d8c72ead0f637f188d01ad4e5bf33644.jpg?AWSAccessKeyId=AKIAI3ATG3OSQLO5HGKA&Expires=1461641484&Signature=88Tgch4D5WrajtwN87aCm8DFy8U%3D

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