I believe the fix for this will be the select "Charter Communications - Digital (non-rebuild)" as your TV Service (instead of "Charter Communications - Cable").
The cable listing only has 99 channels, while the digital listing has the full listing of Charter channels.
To change this from the Slingbox 500 TV user interface, select Settings > Inputs > Reconfigure.
Hope this helps and glad to hear everything else is working perfectly.
Product Manager @ Slingbox
I actually realized that this might be the problem and went back and selected the digital version. Somehow, in this process, I wound up losing the on-screen channel guide. However, all is not lost. I can select the icon of the remote control, and use this to access all of the channels. A little clunky, but, hey, it works. Thank you for your help.
Sent from my iPad