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.