Hi, there. I'm having the same problem. Can't get Wi-Fi Sync working between Android phone (Samsung S6 Plus running Lollipop 5.1.1) and Mac OS X (10.10.5). Definitely on same network but phone sync screen just spins.
@massless: I'm sorry to hear that! Unfortunately without some addition information it's hard to say what might be going wrong. Try the steps in this knowledgebase article, and let me know the results (errors, roadblocks, etc.) as it might point to the cause of your issue:
Was Wi-Fi Sync working for you previously? Are there other devices where it does work? It absolutely depends on your network configuration, so there's a lot that can go wrong. Please let me know what you find. I look forward to hearing back from you!