Why has the Smart side of my Smart TV stopped working?

Why has the Smart side of my Smart TV stopped working?

My Samsung provides cable channels through a Verizon box and and has been providing Netflix, YouTube, etc...through a wireless network. Now, when I go to the Smart TV menu and pick an app, it comes back with check internet service. The TV says it is properly connected and the wireless connection for other devices (including another Samsung) works fine. I have unplugged and replugged the power.

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