This was happening to me for the Thor movie. We fixed it by accessing the “Overview” screen for the movie and then slide over to the “Audio Languages” menu. It lists only one language option for me “English” with an empty circle next to it. It’s not obvious that there’s anything to do but if you use the arrow keys you can make it select the English option. When we went back to the movie, the audio was fixed.
We kept turning on and off the language and close caption options (from English to something else and then back) and eventually it took. But we still get described captions, where print on the screen is translated (and, oddly, when there is something like a recorded voice within the show). First it was German, and now it is Spanish. But we can't get rid of that.
This did not work for me on all three of my TV's that use Roku. Tried multiple times with each one and selected English, but it never stays highlighted, and still that awful audio description stays on. This was for a movie that I bought on Amazon, so I'm extremely irritated about this.