Hi Nicolas,
Good thing is that it works after I have reinstalled it but only when I set the option "Users must be registered to note other comments" to no. However, I only want registered user to vote, so I turned it On and I get the "You need to register to vote" prompt.
Looking at the JS, the hikashop_vote_user_id variable was declared as " ". I have noticed the same case in the demo shop as well. Please have a look at my website and see if things are in order?
P.S. I have PM-ed you my website link because it still under development, so I don't want it to be shared publicly yet. Thank you for your help!