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.
The short story is one day I no longer got On Demand on both of my "legacy" Xfinity DVRs. Yes, several hours of chats; exchanged both DVRs at an Xfinity store; with an in-person Tech to my house as the online/on-screen instructions wouldn't get the new DVRs to even install. The Tech eventually did get the new DVRs to install, but still no On Demand. I ended up ordering a the latest X1 w/2nd TV mini-X1; highest speed home wifi-voice-modem; and an Xfinity alarm system. On Demand now works and, so far, I like this X1 system's user-interface, performance, voice remote, and whatever else I'm getting with X1.
The longer story is one Monday, Xfinity decided to do a 10-hour "maintenance" in my neighborhood by "splitting the node" or somehow re-routing the cable (and maybe fiber optics) in my neighborhood. When the service came back up (it was down from 0930-1930 hours), I had to reboot my Xfinity hardware, but On Demand was no longer accessible with CL-17 codes (unknown service outage) on my two legacy (non-X1) DVRs. Xfinity scheduled me a Technician to come out to fix my problem 2 days later. That Wednesday, I also went in-person to an Xfinity store hoping to upgrade to X1 as I suspected the Technician wasn't going to have a double tv X1 system in his truck. Apparently, it was easiest for Xfinity to totally upgrade my "package" from my old legacy DVRs and 150Mbps voice modem. Although the order was put in, it wouldn't be available until another week when install Techs could be scheduled to install the new 1Gbps modem/alarm/X1. It wasn't too bad. It did take two install Techs ~3 hours to get everything installed.
It was suggested I call the toll-free number to request a credit to my bill for the inconvenience and whoever answered the phone (in an Xfinity Honduran call center) got this accomplished fairly easily.
Xfinity told me I've now been with Comcast/Xfinity for ~29 years. They did get very close to losing my business this time, however. Neither the three Techs, the store Xfinity sales rep, or the call-center customer service reps knew what the cause of the CL-17 no-more-On-Demand was. The three field Techs did suspect some "Headquarters" based software change or possible some unknown hardware-related frequency block when the neighborhood node-split was performed was behind the cause of the legacy DVRs losing On-Demand.
Xfinity gets a grade of "C" from me this time. An "A" would have been to have upgraded me before the neighborhood maintenance; explaining to me that I'll be losing On-Demand if I don't upgrade my services and hardware; and knowing it's neighborhood maintenance was going to cause me problems instead of me finding these problems and going through Xfinity's "hoops" of getting this all done. Xfinity recently began, once again, going to people's homes for service & install work with this Covid-pandemic situation going on.