THE SOLUTION IS VERY EASY: Turn on your Samsung smart tv, and then unplug it. Wait at least 30 seconds then replug it. Try to make the connection again to the router. It works.
The TV software occasionally has to be reset this way. I found this solution after doing extensive searching, someone else shared it on a site, and the method worked. For awhile, the tv would not recognize my router with its password or Smartview on my smart phone. This method got the tv wifi card and tv software back in sync.
Definitely try it before the more elaborate things that take time ... !!