If you only have Alissa.7z.001 and no other parts, the download is likely incomplete, and the file cannot be opened. To help you further, could you tell me:
If you don’t have it, download and install it from the official website . Right-Click Alissa.7z.001 : Select the 001 file only. Alissa.7z.001
Choose 7-Zip > Extract Here or Extract to "Alissa" . If you only have Alissa
Ensure all parts are in the exact same folder and have the correct names before the .7z.001 extension. the download is likely incomplete
This happens if you are missing subsequent parts (002, 003, etc.) or if one of the parts is corrupted.