CL-0x000f indicates a communication problem with their On Demand server.
Call them at the phone number on your bill or 1-800-Comcast, or chat with them using one of the "Trouble" options at https://www.comcastsupport.com/chatentry/. Ask them to check the account setup and send a refresh signal to the cable box. If they can't fix the problem remotely, insist they send a tech out to identify the cause and correct it.
If the tech finds bad coax, splitters, amplifiers, or connections in your home (even if Comcast originally supplied them) you'll probably have to pay for the visit unless you have or sign up for their Service Protection Plan (https://www.xfinity.com/support/account/service-protection-plan/, about $6/mo) and keep it for at least 60 days. If the trouble is due to a faulty Comcast cable box or DVR, or anything outside your home, you shouldn't be charged.
I did all of that. In fact the technican came to my home and didn't fix the problem. Comcast has sent several refresh and restart signals, and I even did so through my account, yet the problem persists. The tech allegedly changed the splitters and still here we are with no On Demand for all 3 boxes. And Comcast better not charge for the visit as they never fixed the problem!