have you tried using Smart View or just the App specific casting features (such as youtube's chrome cast)?
Could also be a compatibility issue... if you think it's an issue after trying some of these, you can contact Samsung using Samsung Members app
hmmm. that's an odd one... I'd ask Samsung if they know a fix for this or not. Could be that either the TV or the phone just doesn't have the right hardware to connect to each other or something of that sort. So, going back to the initial comment, try using the Samsung Members and see what they can do for you