I stopped really working on this addon about 9 years ago - the last release was 7 years ago. It's discontinued. I'm not planning to fix the add-on to make it work on modern versions of Thunderbird - I'm surprised it worked at all for many years. It's open source - fork it and fix it if you want. The successor addon can be found at: https://addons.thunderbird.net/thunderbird/addon/attachmentextract