Many unofficial archives (AIO/Repacks) require a password. Check the source where you found the link (often the website URL or the uploader's name).
If you are sharing this file or looking for a way to explain it to others, here is a helpful post template: AIOURDR2DD.part04.rar
Double-check that all parts are named exactly the same except for the "partXX" suffix. Many unofficial archives (AIO/Repacks) require a password