I am also having the same issue which caused some frustration as I would like to fully utilize my new graphics card while watching movies.
I really like watching movies and TV shows with my wife in our free time, and we also enjoy watching high-quality UHD videos of our cats. Recently, I purchased a new graphics card, the RX 550 D5, which has built-in H256 decoding, in order to improve our viewing experience.
I prefer to use the Windows App called Movies & TV. However, I have been facing some issues while trying to add the Movies & TV app to the graphics card. Even though I have access to the Appstore folder, I have not been successful in adding it.