I uploaded a .7z file online several years ago and recently tried to download it. File contents should be .ut3 and .ini files. No .exe or .bat etc...It will not unpack. I used the very software i used to pack it 7zip, to try to unpack, no luck.
I have discovered that the header is corrupt and possibly the footer from this guide to recover 7z files.
I tried tech support in reddit and didn't understand the suggestion: