Not sure why that is the case, it looks like I can vote. It does say your not supposed to ask friends to vote in this competition to make things more fair.
I did just try to rate a project, and yes you are correct. There definitely is some kind of error occurring. I will look into the matter and contact itchio support if necessary. When I try to leave the review it says what you see below despite that criteria being marked:
Please check the information you provided
- no score for Relevance to Theme [How well the Problem and Solution is Communicated]