1. Setup again, tell tv to use Ethernet then back to WiFi.
2. Check with Samsung on firmware updates, always factory reset after this and try again.
3. MUST BE UNDER 20 FEET TO ROUTER. It does not matter it worked before. Must be under 20 or they won't help.
4. Replace WiFi with powerline or other WiFi to Ethernet solution.
5. The TV's date/time SHALL be correct or you may get connection failures.