I have just tested that site and whilst the track naming is a bit spotty, the downloads themselves work fine.
What version of Mac OS and Jaksta are you running? If you are not running the latest version of Jaksta then updating that would be a good start.
If it still does not work can you please provide me with a direct link to video/song you are having this issue with so that I can test it?
From Liam @ 10 Oct 2017 11:10