check the cable connection on the switch attached to side stand ... it could be loose or corroded ... check that the sensor plunger is moving freely ... use some WD-40 on it
check the wiring between ECU and switch connector ... it could be damaged or broken
check that all cable connections to the ECU are attached firmly
you may enter diagnostic mode on your bike display and notice if the code no 20 is changing its value when putting side stand from resting position to drive position ...