This error can occur if for some reason you have been issued a new passphrase/reading key since you originally downloaded and opened the book. Please re-enter your new passphrase/reading key from your eBooks.com account and your should regain access to the ebook.

If you are an Arch Linux user it can also be caused by installing the AUR package here. A customer that had installed this package received the above error message. They then went to https://thorium.edrlab.org and installed the official AppImage and this resolved the issue.

Another user on Ubuntu 24.04.4 LTS reported the same issue using Thorium Reader v2.2.0. They went to https://thorium.edrlab.org and downloaded the '.deb' file and installed it and it resolved the issue.

If this doesn't resolve the issue there may be a temporary issue with the issuing of the reading keys on the eBooks.com website. Please complete our support form to submit a ticket to our customer support. Please be sure to mention the title of the ebook that is having the issue, and attach a screenshot of the error.

In the meantime, while we resolve the issue, you should still be able to access your ebook on Thorium Reader if you import your eBooks.com bookshelf as a catalog using an OPDS feed. The reason why this will still work is the reading key is embedded directly in the OPDS feed. If you haven't already linked your eBooks.com bookshelf as a catalog in Thorium Reader, instructions on how to do so can be found here.