Can't download a game pass game on Xbox One

Can you please check Troubleshoot game or app installation problems on Xbox One | Xbox Support for further assistance.

You can't merge the accounts, but you only need one Game Pass subscriber per Xbox. If you designate that Xbox as your home console, games you download from Game Pass can be played by other users on that same Xbox even if they don't subscribe to Game Pass.

https://beta.support.xbox.com/help/hardware-network/console/my-home-xbox

When you go to the game page on Microsoft Store or Xbox App to download it you can't download it? It shows you to buy game pass or buy the game?

Game Pass Games are subscription based games, and only Backwards Compatible 360 games for the Xbox One work with Game Pass.

If you have Game Pass Ultimate, which includes Gold, you can keep the Games With Gold for Xbox 360. But with only Game Pass, you can't play any backwards compatible games on the 360, and on the Xbox One, the games stop working after your Game Pass trial
ran out.

So in short: No, you can't keep Game Pass Games, be it Xbox One or Xbox 360 games. And Game Pass doesn't work on original Xbox 360 consoles at all.

The Game Pass games can't be downloaded from the Windows Store, you need the official Game Pass App.