Ask HN: Why does exact keyword search break on prime video app?

Hi, I am a newbie to search algorithms. I was looking for a movie available on prime video app and the exact search term returns zero results. The same keyword works fine on amazon.com website and even searching for only one word returns results on the app. What makes the algorithm break for an in-app catalogue search like this? Another question being how do they build the search corpus for generic keywords like 'keanu reeves action movies'?

Screenshots from the app are here:

https://imgur.com/a/pK95Umx