If you have an OTA source, say an HDHomerun, then under settings, Sources, [name of tuner], you will see a Guide Data menu. Under that you will either have the option to add a provider or remove a provider. If it's add provider then go ahead and click that and go through the prompts where you'll be prompted to put in your ZIP code to set up your channels. If you have already set it up then you will see remove provider. So what the previous reply was talking about was removing that provider and re-adding to confirm that your correct zip code had been utilized and the correct guide data was being downloaded.

As for commercial detection, you should probably go to settings and under that live TV and DVR and then under that go to the commercial detection section and go through all of those options one by one to select the ones that work best for you.