There is a nationwide outage with Comcast. I got a "subscription required" message when trying to watch On Demand shows so I called Comcast. That was the answer I received. They said the outage should be over at 4:30 pm pst. Type in Comcast Nationwide Outage into Google and you'll find a bunch of info on the outage. Some Comcast employees are aware of it, others are not. Comcast website does not discuss the outage, nor did automated phone line (which surprised the cs rep I spoke with). Comcast needs to get their stuff together and keep their customers informed.
The "subscription" notice has nothing to do with an outage. What that means is that the particular channel you are trying to view is not in your tier and in order to be able to watch that channel you would need to upgrade to that tier at an increased cost.