Certain Titles Appearning on Store Website but not in Console App Store

I'm not certain that the iOS app will let you purchase anything via the App due to Apple's App Store policies. You'd have to purchase on the console or website. The Xbox Store is available online for purchases here: https://www.xbox.com/en-us/games/xbox-one

Well typically you want to use the Xbox app rather than the ms store

For one compatibility

You can buy the pc copy or the console copy on the ms store hence why certain games like console only or multiplatform games need to be purchased in the correct store

So that you don't buy the wrong copy

And games.require the Xbox launcher or play anywhere titles which don't matter which platform

Also ms store supports buying physical items like disks consoles etc

This is how it was solved for me.

From Dolby access website:

Open your console web browser and search for "Get Dolby Access." You should get a link that is titled "Get Dolby Access - MS Store" or similar. The URL will be a Microsoft URL, not a Dolby URL.

2. Click on "Get the App."

3. Choose to accept when the message prompts you to launch the Store app.

4. Download Dolby Access or Headphones from this new instance of the MS Store. If already purchased, choose "Launch."

If he is on a child account, he would need to make the purchase on a 360 console. This is due to certain restrictions in the 360 store that do not transfer over to the One or website.

The version through the website would be the console version of the game. You would need to have purchased the PC version of the game and install it from the Microsoft Store app or Xbox app, not the website.