Unless I am mistaken there is no search in the On Demand section. I have tries all suggestions from the internet but nothing works. For example - "hit search, red button etc" does nothing. I wanted to watch Salvation from the first episode, I finally did a chrome cast from my computer. It shouldn't be this hard;
Usually I just do a regular search, then go to episodes (at the top), & On Demand availability shows in the list. Not all networks provide On Demand programming to Dish, some only have limited shows. CBS wants people to subscribe to their All Access paid service or use their website, it's not up to Dish.