Hello, constantfrustra. Welcome to the Xfinity Forums!
You do need to be subscribed to the network that is airing the on-demand content you want to watch. If your current service plan does not include many of the networks you are looking for, I would be more than happy to help find you a new service plan that better fits your needs. Please send me a private message with your first and last name so I can assist.
To send a private message, click my name "ComcastTambrey", then click "send a message".
constantfrustra, as I have not heard back from you in some time, I have closed this thread to further comments. I hope you were able to find the best solution so you could still watch the episodes you were looking for, but if you still need assistance, please feel free to start a new thread.