The distant to the router must be about 20 feet to start with. There are also issues with some routers. Given only the details so far, I wonder if this is wireless and over 20 feet to the router.
I have a VIZIO smart TV and even when the settings show I am connected via Wifi, my internet apps stop working adn show disconnected. The ONLY thing that is successful is doing a reset to factory defaults, I have to then set up again, enter my password three times (it rejects it the first two times and won't connect) and voila, I can get Netflix, but only for THAT viewing session - next time, it's back to square one. Should I return the TV?