You need to connect your NVIDIA and Xbox Accounts to enable Game library sync.
1. On any GeForce NOW app, go to Settings > Connections > Xbox > Connect

2. Click CONNECT for Xbox, which will launch a web browser to a Microsoft website.
NOTE: Click the “BACK” button if you do not see the correct Microsoft account that you want to link with your NVIDIA account.

3. Login to your Xbox account to complete the account linking step. If your account supports two factor authentication, you will do this during account linking.
NOTE: Linking your accounts on TV platforms will generate a QR code which you can scan with your mobile device to complete the account linking.

4. After linking your accounts, you will be able to verify that your account is linked in the GeForce NOW app under Settings > Connections.
