Old games becoming purchasable on xbox store.

That would be something that's up to the publishers/developers. There are many reasons they may not be available though.

Left 4 Dead 2 is available to purchase digitally. https://marketplace.xbox.com/en-us/...-9115-d802454108d4?DownloadType=Game#LiveZone

So you're saying that I had to have purchased both the base game and expansions from the Xbox store in order for TTK to become available?

All games are Xbox One games, some purchased used at a game store, some brand new just out games. All have worked and been playable only for hours later or the next day become unplayable.

Games we purchased online work fine also.

Hello again,

As Tezzarrific mentioned before, it appears that Mortal Kombat 1 is not available on the Microsoft Store or Xbox App on Windows. You will need to purchase it from different platforms or launchers.

It is unlikely that the game will become part of Xbox Play Anywhere in the future. Generally, games become part of that catalog from their initial release, and it's not common for them to be added later. Additionally, for a game to be eligible for Xbox Play Anywhere, it needs to be available on the Microsoft Store on Windows, which is not the case here.

That's the issue. Because of the changes in the store, purchases made in the new store while in the preview program cannot be shared. So you won't be able to share the games until the update becomes public.