I am assuming that by “instructions”, you are referring to HanDuet’s “The Ultimate Introductory Guide” for obtaining Harmy’s DEEDs.

I can only think of four possibilities:

One or more of the RAR parts are missing;
You accidentally entered the wrong password (ensure it is “harmyDEED”);
The Mac RAR unpacker doesn’t like these particular files for some reason (perhaps it doesn’t cope with multi-RAR archives such as these);
Your downloads are corrupt.

The first two are easy enough to check. Afterwards, I would try another RAR unpacker for your MAC, or copy the files to a PC and try either 7Zip or WinRAR. I have used the former successfully. Failing that, I suspect you’ll need to download the RAR files again. Keep the original downloads and compare their checksums with your new downloads so you can see which RAR parts might be the problem. A good, free program for this is “MD5 & SHA Checksum Utility” by a chap called Raymond.

Good luck!