The BBC iPlayer app is only available inside the UK. If you are not located in that location or have recently moved out of the UK then the app will no longer be available from the main menu of SHIELD TV.
If you are located in the UK, please ensure that Location Services is enabled. To do so, navigate to the Settings menu and then into the Personal->Location menu and ensure it is enabled.
If you prefer not to use Location Services, please ensure that the device language selection is set to "English (United Kingdom) (GB)". To do so, navigate to the Settings menu and then into the Preferences->Language menu and select the language from the list.