Why is the green light of the sending card not flashing?

1. The DVI cable of the sending card is not plugged in properly. Reconnect the DVI cable.
2. The display mode of the computer is not set, and it is generally set to copy mode. If there is no setting option, it means that the driver of the independent graphics card is not fully installed, and reinstall the driver of the independent graphics card. Set to copy mode.