It may be that you need to have your TV do a scan for the channels that are available. I think that most TVs can probably do this, since it is a feature on our 2008 model set. Check the instruction book for your TV, if you can find it. If not, it will probably be available online.
Check to see if your remote has a button marked something like "Menu" or "Menu/Setup". On the menu, select "Channel". Look for something like "Auto Channel Memory", then select "Air" or "Cable", depending on how you receive the TV signal. Next, you should be able to start an automatic search for available channels, which might take up to a couple of minutes. That should find both the primary channels and the subchannels, like 8.4, which you will then be able to access.