Recently I encountered the same problem but have fully paid my memberships.
We have the same issue with Prime and Netflix and pretty much all the other apps. Contacted Samsung 5-6 times about it and followed all advice given to no avail. After a bit of digging we've discovered that it could possibly be an issue with Yahoo who write the apps for Samsung and Sony. There's some kind of dispute between them and the apps are no longer supported. I'm taking my TV back!
We've been enjoying the hell out of some Netflix and amazon prime shows for the last few months, but as of about two or three (?) weeks ago, they just STOPPED working.
[And, yes, our wi-fi is connected, and we are still able to access YouTube, etc]
Anybody know of a fix??
As stupid as this sounds, it was recommended by samsung support and it worked for us !
While the tv is on, unplug it from power for 30 seconds to 1 minute. Plug it back in and Netflix and Prime should be back !
Seem it builds a static loop after a period of time and causes a malfunction with smart hub.