;TLDR version:
It appears the SHOWTIME “app” that came preinstalled on my Roku enabled TV is for people who want to just buy Showtime to stream. You want the Showtime Anytime app if you get Showtime through your cable provider.
Long version:
Several months ago I got Time Warner Cable with HBO. Shortly after I bought a new TV (Hisense Roku Enabled 40" for $300 from Best Buy. I love it.) On the main menu of the TV are icons for the cable box, HBOgo, Amazon Prime, Hulu, Showtime, Netflix, etc. Through the cablebox I could go to HBO on Demand and watch the last season of Game of Thrones, but to binge watch it from the beginning I needed to go to the HBOgo app (which is streaming; not coming from the cablebox) and tell it that I had HBO from TWC and I was good to go. It took 9 days to watch 50 hours of GoT.
Last month I got a Christmas gift from TWC: a year of Showtime for free. I could watch the last season of Shameless by going to the Showtime on Demand channel thought the cablebox. Also, I could go to showtimeanytime.com on my desktop computer and watch all episodes. However, I couldn’t get onto the Showtime ‘app’ that came preinstalled on the homepage of my Roku TV to watch all seasons on my TV. Showtimeanytime.com wanted an activation code from my TV to activate a new device, buy my TV wasn’t giving me one. When I (painstakingly) entered my showtimeanytime email address and password into the TV, it only gave the options of starting a free month trial or logging in on another account.
After a call to TWC’s tech support, the girl and I figured it out together. On my TV I deleted the Showtime icon (initially the idea was to delete and reinstall: SOP for tech support). I had to search for “sho” and there were 2 options: “SHOWTIME” and “Showtime Anytime”. I added “Showtime Anytime”. It asked who my cable provider was, I told them and it gave an activation code that I plugged into my computer.
Now my TV is activated and I’m about to watch Season 1, Episode 1 of Shameless on my TV.