It sounds like the issue is that both parts of the split archive weren't downloaded correctly. If you're seeing an error like "same volume can't be found," it's likely that both files are named the same—or the second part is missing entirely.
Please make sure you've downloaded both Part 1 and Part 2 of the archive and that they’re in the same folder before extracting. Also, don’t rename the files, as the extraction software needs them to have the correct names to combine them properly.
Let me know if you're still having trouble