Follow their suggestions and if Samsung can't fix it, go for a refund as it's defective.
I recently bought a Samsung UN55KU6300 Smart TV. Initially, when I tried to stream from youtube app on my iphone to the TV, it was working well. Also, Samsung Smart View was working fine on my iphone, android phone and laptop. After a few days , Samsung Smart view stopped working on all the devices. Also, when I tried to stream youtube/netflix from my phone, it wasn't showing the Samsung TV as an option. Then I changed some settings on my network and turned off all firewall settings, still not working. Then I created a hotspot from my iphone and connected the TV, android phone and laptop to this hotspot. Voila! everything worked! . But ofcourse , I can't use by cellular data all the time. Now, I tried connecting a new android phone to the network. This phone wasn't earlier used to stream to the TV and wasn't connected to the wifi network since i bought the TV. And weirdly, I was able to cast/stream from this phone to the TV. So basically, my mind is blown right now and I am willing to try any possible solution.
FYI: The samsung tv firmware was the latest and the same throughout this.