CL-17 error

About a week ago, our On Demand function stopped working.  We continually receive an error message referencing CL-17.  I have followed the directions on multiple online forums by disconnecting, then reconnecting our box, to no avail.  One of the remedies was to swap out the cable box.  I have an in-person appointment at an Xfinity store to try to do so.  If anyone has any other suggestions to resolve this matter, any help would be greatly appreciated.