You're welcome! (I am a cybersecurity engineer so when I saw the reply I had to say something!)
For onlookers, when you add an IP to a DMZ it mean, for this IP address, turn all the security off. Just let everything connect however it wants (from the world outside your router, which is likely your service provider, i.e. the wider internet.)
I know that means you need to find another solution for your TV, which is hugely annoying (I have a Samsung TV and it drives me mad) but it is better than effectively shouting your bank account details across a busy pub.
For me, as in an earlier reply, I found that it was the DNS resolution which was causing the TV to not work. This is a complex problem that requires some skill and knowledge to fix (until Samsung quietly change something.) Unfortunately, my advice is to contact Samsung or hope that your country has something like we have here (The Consumer Rights Act) which means products have to work, else you're entitled to a refund.
