When I connect to DJI Assistant 2 my drone doesn’t stay connected,

When I connect to DJI Assistant 2 my drone doesn’t stay connected,

My drone does not stay connected long enough to DJI Assistant 2 for me to calibrate the vision sensors, it says Lost connection, ensure flight controller is connected to your computer and the Mc output on the left side shows a red cross. I would like to know is there a way for me to test my flight controller board before I replace it.