LG TVs are not a bad purchase, they provide their customers the world-class picture quality. And if you are concerned about getting the spectrum app on your LG tv then there are other ways to get it.
The most Simple and Secure way to get Spectrum App on LG Smart tv is through a Streaming device like Roku, Chromecast, Airplay, or Firestick. You can also the App on Xbox one or by downloading an APK file.
You also said that you have a Spectrum cable box and if it is not working properly then you can do some diagnosis.
You can Reset the Spectrum Cable Box through the website or spectrum app.
Rebbot it manually
If you see an error code on the screen, you can contact customer support.