Showtime Now Through April 19 promotion not working?

I have  Internet-only service. In the Xfinity Stream app, I see a promotion Showtime Now Through April 19.

When trying  to access any Showtime content other than free first episodes (like The Affair Season 5 Episode 11) I get the following error:

"Showtime:  Subscription Required :: 12013
Your subscription does not include this program, or it is not playable on this device. Please choose another program."

I've tried 3 different devices (iPhone, iPad, desktop computer).

I was able to watch this content about a week ago, then the error above started to appear.

Question: Is this content included with the April 19 promotion, or are only the free pilot episodes included?