That contest is powered by Woobox, I see. They are semi decent at blocking bot attacks. There's a simple free Python script to defeat it and do vote stuffing for you though.
https://github.com/alxgmpr/Hunger
You just need to provide a list of proxy IP addresses (Google: "Free Proxy IP list"), and plug in the ID of the contest, and let it rip.
Now the bad news.. you need to know how to install and run Python and scrape the contest ID from the vote link.