If your Passphrase is not being accepted you may or may not be receiving this error message: No stored passphrase fits the publication, or the entered passphrase is wrong.

Linux users have previously reported this issue when installing Thorium Reader from their Linux distribution's own Package Manager. The version of Thorium Reader in the Package Manager is outdated and still using an older LCP Profile (like 1.0) when we (and newer versions of Thorium Reader) are using the newer LCP Profile 2.9.
 
Please try installing the latest Thorium Reader AppImage or Debian Package from the developer's website here: https://www.thoriumreader.com/en/download/
 
Once installed, this version of Thorium Reader should definitely accept your LCP Passphrase / Reading Key.

If you follow the above instructions and are still having difficulty please contact our support team, please let us know what Linux distribution you are using, what version of Thorium Reader you have installed, and please include a screenshot of any error message you are receiving.