I think most of us has struggled with this issue at least once in the past. If the ports are open, and you have it properly configured (by the way Notification Server handles WOL differently than Deployment Server), WOL will work, sometimes, and maybe.

So, you can install Wireshark and trace the packets to see why they are not making it, but other than the above ideas (ports and infrastructure, meaning the WOL proxy) not much more can be done.