If compass calibration is required, an alert will be shown in your capture app as well as in the DJI Go app. Some drones also cannot take off when compass calibration is required. However, calibrating the compass may not always be necessary. As a first step, try moving your drone away from metal objects, reinforced concrete and electric equipment. If the error persists, switch to the DJI Go app, then follow the DJI Go app instructions to calibrate the compass.