a Green LED light would be an indication that the device is recognizing USB 2.0 bandwidth and power. Under USB 2.0 conditions, its maximum supported frame rate at Full HD is between 4 and 12 FPS. Under standard definition video it is possible to achieve 30 FPS.
Please ensure your AV.io is connected to a USB 3.0 port in order to get full resolution and performance capabilities. If you are connecting the device to a tablet or small form-factor laptop, ensure the AC power is connected. Depending on the USB throughput you may need to use a powered USB hub between AV.io 4K and the computer.
The device is designed to utilize 100% of the USB 3.0 bandwidth. Please ensure that no other video or audio capture devices are utilizing the same USB buss. It can cause performance and power issues for the device