The password algorithm changed in the lasts versions of Whatsapp, at least in iPhone. You can get a Base64 of the md5 from the application directory, but it doesn't match the imei or mac md5. I am trying to break mine with hashcat to see what kind of pattern it follows.

I guess you are trying to do the MD5 yourself, while you should simply just enter the mac address with the : . The script will automatically generate the hash for u.