The first thing to do if you’re seeing Hulu playback errors on your Switch is to run the internet connection test:

• If you have any apps or games open, press the home button and return to the home screen.
  From the home menu, navigate to System Settings > Internet > Test Connection.
  Verify that the internet connection is working and that the download speed is sufficient for streaming Hulu videos.If your internet connection is fine, try closing and restarting the Hulu app:
• Press the home button to return to the home menu.
  Highlight the Hulu app and press X.
  Select Close.
  Restart the app and check to see if you still have playback errors.
  The next step is to check for updates to the Hulu app:
• From the home menu, select the icon for Hulu.
  Press the + or – button on the controller.
  Go to Software Update > Via the Internet.
  If you still experience playback errors, make sure your Switch itself is up to date:
• Press the home button to return to the home menu.
  Navigate to System Settings > System > System Update.
  The last thing you can try is to uninstall the Hulu app and re-download it:
• From the home menu, select the icon for Hulu.
  Press the + or – button on the controller.
  Go to Manage Software > Delete Software.
  Open the Nintendo eShop and re-download Hulu.