The TV needs a strong Wi-Fi signal. Note that the Wi-Fi range of a TV can differ from smaller devices, like computers. To check the Wi-Fi signal:
• Press the “Home” button on the remote control of the television and select :
[Setup] > [Network Settings] > [View Wireless Settings]
• The Signal strength should be above 3 stripes out of 5 (60%).
Try to decrease the distance between the TV and the router, or preferably try a wired connection, which is more stable.