You need to connect your NVIDIA and Battle.net Accounts to enable Automatic Sign-in and Game library sync.
1. On any GeForce NOW app, go to Settings > Connections > Battle.net > Connect
2. Click CONNECT for Battle.net, which will launch a web browser to the Battle.net website.
3. Login to your Battle.net 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.
Note: if you have previously connected your Battle.net account, you will need to complete the following login screen the first time you launch a Battle.net game to enable automatic login on future launches.