Arduino Board Manager Error

Hi,

I am very new to programming as a whole, and only received an Arduino a couple of days back. I have recently been trying to install the Sodaq Mbili Board Hardware. I have tried to do this be navigating to preference and putting in the download URL (http://downloads.sodaq.net/package_sodaq_index.json) under Additional Board Manager URL. However, whenever I go into Board Manager to download it, I am greeted with:

Error downloading http://downloads.sodaq.net/package_sodaq_index.json

I am really confused at what I have done wrong, and really need help on how to fix this issue.

Thanks in advance.