XiD-P box defaults to sd

My mom lives in an assisted living community. She has an XiD-P box manufactured by Pace with an HDMI cable running to her HD TV. The problem is that every time she changes channels, it defaults to an SD channel. The channel banner on the top of the screen has the option to select HD, but you need to do that every time to get the HD channel. We have her setup with a simple remote which doesn't have a select button, so she winds up only being able to watch in SD. In all the Google searches I've done, the instructions to default to HD are to go into settings and select Prefer Best Resolution. This is not an option in anywhere in her settings. When you press the xfinity menu button, you only get guide, audio, hdmi, channel lock. There are no preferences or general sub-menus. Please help.