Here are some steps you should take to troubleshoot your Smart TV not displaying 4K content properly:

1. Make sure your TV is connected to the internet
2. Verify it is connected to the correct input (HDMI input etc)
3. Reboot or reset your TV to ensure any updates have been installed
4. Check your TV settings (resolution, HDMI mode etc)
5. Verify that the content you are trying to stream or watch is 4K UHD
6. Confirm 4K is enabled in your account settings with your streaming service