Is your box on the list here? I am guessing the new boxes can use a new guide depending on if available in your area. This "Contour Stream player" probably doesn't have that option because it runs as a app instead of natively. Maybe there is a way to get it to run normal Contour instead? Hopefully a moderator can help more.
The menu system and online experience didn't change at all, I was pleasantly surprised in that regard.
The brand shows as SERCOMM on my TV devices account page (not listed on the link you sent).
Everything looks the same as on the other boxes, just don't see a way to set the default channel. It starts up on some page with the weather and ads (as my Dad describes it, he's always on the TV first each day, haven't seen it myself). We were hoping to get it to start up on a preferred channel as the old boxes did.
The brand shows as SERCOMM on my TV devices account page
Not to be a pain, but could you look on the unit itself for a model number? If nothing else, it would document the problem for others. I found these but it is possible Cox got something new/proprietary from the manufacture.