Dear Amazon, the Prime menu is fairly awful - especially trying to find a way back to a previously watched series.
I'm not praising that app at all btw, that's just why I think the award for worst app goes to CBC gem on the Fire stick. It shows you which episodes you watched. Past tense. To watch the next one you have to search for the show again and navigate to the episode. Why on earth would anyone want that?!
For this reason I only watch Amazon originals on Prime, since I know they’ll be available.