Error extracting a RAR archive: "is not RAR archive.No files to extract"

I have multiple huge RAR files that are separated into 6 parts.Some parts are completely downloaded,some not just yet.When I try to extract the fully downloaded archives,I get this:

$ unrar e whatever.rar
...
whatever.rar is not RAR archive
No files to extract

BTW x and even t switches don't work for me.The interesting fact is that the l switch can successfully list the contents:

$ unrar l whatever.rar

Archive: whatever.rar
Details: RAR 4, volume, recovery record, lock

 Attributes      Size     Date    Time   Name
----------- ---------  ---------- -----  ----
*   ..A.... 2097555771  2015-02-23 11:07  whatever/1
*   ..A.... 2097957006  2015-02-23 11:09  whatever/2
*   ..A.... 2097895618  2015-02-23 11:09  whatever/3
----------- ---------  ---------- -----  ----
           4195852624  volume 3          2

I've tried that using **Ark**.It says:

Loading the archive ‘whatever.rar’ failed with the following error:
Failed to find all archive volumes

Can it be because of the fact that not of all the archives(i.e parts) has been downloaded yet? Any help is much appreciated.