Clicking on Vote/Endorse does not seem to have any effect. If these button-looking elements are meant to be more like "Headlines", please remove them. If they are meant to trigger an action, I could try to find the reason for it.
Topic on Talk:Developer Wishlist/Flow
I get a "Vote for this proposal: [Cancel] [Vote]" overlay popup in FF51.
They are meant to trigger MediaWiki:Gadget-addMe.js (which was adopted about an hour before voting started, in a rush job, and so aren't high quality). Debugging is much appreciated. You can see from the page histories that it works for most people so I would suspect some browser-specific issue.