Diagnosis
The built-in Wi-Fi receiver in this model isn't the strongest, and it's prone to interference, especially if your router uses a crowded channel or is too far away.
How to Fix It
First, reboot your router. Then, on the TV, go to Menu > Network > Manual Setup. Change the 'Wireless Channel' from 'Auto' to a specific number, like 1, 6, or 11 for 2.4GHz. If you're using 5GHz, try a channel in the lower range. This prevents the TV from constantly hunting for a signal. Finally, perform a 'Soft Power Cycle' in the Admin & Reset menu to clear the network stack.
If That Didn't Work
The most reliable fix is to bypass the Wi-Fi entirely. Get a simple USB-to-Ethernet adapter and plug it into one of the TV's USB ports. The TV will automatically recognize it, giving you a wired connection that's far more stable for 4K streaming.
Heads Up
Avoid placing soundbars, Bluetooth speakers, or even your cable box directly in front of the TV. They can physically block the weak Wi-Fi antenna, which is located along the bottom bezel.