I have just got the gamepass and bought the Age of Empires III game but the xbox app on pc...

Yes, the game I used to get the error message was Twelve Minutes, but I also got the same error from all the gamepass games I tried to play on PC. (Doom Eternal, Carrion, Project Winter, and Age of Empires III: Definitive Edition).

Some of the games on PC are availble on gamepass on Xbox however not all of them such as Age of empires as it requires a mouse and keyboard. Also gamepass for PC is a separate subscription to Gampeass, you would either have to buy another gamepass subscription
or get Gamepass Ultimate which works both on PC and Xbox

Hello Joshua G, My name is David. I am an independent advisor, happy to help you today.

first Verify your Xbox Live Gold subscription To access multiplayer in Age of Empires III games through Xbox Game Pass, you may need to have an active Xbox Live Gold subscription. Check if your subscription is current and active. If you don't have a subscription, you may need to purchase one to access multiplayer.

y Restart the game and the Xbox Game Pass app: Try closing the Age of Empires III game and the Xbox Game Pass app completely and then restart them. Sometimes restarting the game and app can resolve temporary issues and allow the multiplayer option to be available.

Best regards.

I just got age of empires for my PC and do not understand where my product code is

There is many games that are made just for PC and have been added to Xbox one.

I just think if it's made for PC like the Age of Empires then it should stay on PC unless they allow Keyboard and Mouse to play it on Xbox one