On Demand not working

We have not been able to access On Demand for a few weeks.  We get an error message CL-17.  We've tried trouble shooting but it didn't help.  I even talked to someone from Comcast who had no luck either.  They were supposed to send someone out to the house last week, but they couldn't make it in the time slot and we had to cancel that.  We've tried the refresh, but it says our main TV box is offline.  We only have one TV and box, so don't know what to do.  Any ideas?