Books in Calibre are not available for reading

Problem Description
Books in Calibre are not available for reading.

Steps to Reproduce

  1. (Login to FreedomBox.)
  2. (Go to Calibre Page with books.)
  3. (Click on the book.)
  4. (Click Read.)
  5. (None of the books have been opened.)

Actual results
I get an error with the following message: see screenshot


  • FreedomBox version: 20.21
  • Hardware: Raspberry Pi 3 B+
  • How did you install FreedomBox?: downloading latest stable image from


These are screenshots on an iPad with Safari.
On PC with Windows with Chromium or PaleMoon browsers, I get the message: «This browser does not support Application Cache so offline access to caliber will not work. Some browsers only enable Application Cache over HTTPS–connections, so you may have to setup HTTPS for your caliber server».
When trying to open the book (online, not offline), the same errors as in the screenshots.
On PC with Ubuntu and Firefox I get the same thing: “Could not open book. You must allow caliber to use IndexedDB storage in your browser to read books”.