If you get a "Can not open file" error, the file may be corrupted, incomplete (if part of a multi-part archive), or you may need a newer version of 7-Zip.
What is the (e.g., a game mod, a book, software, data)? I can provide more specific instructions on how to use it. Irk17.7z
If an application (like Calibre) does not recognize .7z , you may need to unzip it first and re-zip it into a .zip format. If you can provide more context, such as: Where did you download or receive this file from? If you get a "Can not open file"
It supports high compression ratios (using LZMA/LZMA2), strong AES-256 encryption, and file sizes up to How to Open/Unzip Irk17.7z If an application (like Calibre) does not recognize
Here is a general guide to handling .7z files like Irk17.7z : What is a .7z File?