Sorry for the inconvenience. According to your feedback, we suspect that the shield is sleeping.
When the activity starts, all devices are powered on, but Nvidia shield does not have a power key, so there will be no action. The command wake-up device is required for normal operation.
You can try the following operations. On the activity page, edit -- startup settings, add a command, and add a shield command, such as medu (or other wake-up commands), to wake up the shield