Must be a dozen threads in this forum about CL-17, which appears on my TV right now.
According to the other posters, they wasted hours, as I have, talking to Comcast support, unplugging and plugging in their cable boxes, etc.
Apparently it is a problem that needs to be solved centrally by Comcast with some programming or setting magic, and only a few techicians know how to do it. So you can spin your wheels for a long time before hitting upon a Comcast support person who knows what needs to be done.
A Comcast representative responded to the most recent thread with a pointer to this trouble shooting page https://forums.xfinity.com/t5/TV/ANSWERED-Xfinity-On-Demand-Error-Codes-and-Troubleshooting/ta-p/323... , then closed the thread as answered BUT THAT PAGE DOES NOT REFER TO CL-17
If you get Error Code CL-17, you can expect the usual runaround from Comcast support. You'll just have to keep at it until Comcast fixes it in their central programming. You know, the usual -- phone over and over, keep telling the same story over and over, go through the useless troubleshooting steps. Each call will take about an hour. Eventually, Comcast may or may not fix the problem that is on their end.
You have no choice except to find another TV vendor -- which is entirely doable these days.
I'd really like to know what is the central issue that Comcast cannot bring itself to fix so as to prevent so many customers to be inconvenienced even though they're paying Comcast's exorbitant fees for cable TV.
The resolution of this problem is to get an updated X1 cable box.
Recent changes in the way Comcast tranmits TV made some cable boxes obsolete.
I got my new box (includes DVR) today.
New design of the channel guide and On Demand uses smaller type and is much more difficult to read unless you have an enormous TV.