Mozilla removed it. This can happen when issues are found during the review of the extension or theme, or the extension or theme has been abusing the terms and conditions for addons.mozilla.org. The developer has the opportunity to resolve the issues and make the add-on available again.
Mozilla 已将其下架。这可能是因为在审核扩展或主题的过程中发现问题，或是该扩展或主题违反了 addons.mozilla.org 的使用条款和条件。开发者会有机会解决问题，并重新上架。