Pixhawk can't connect to qgoundcontrol

Hi , I have a problem after update firmware pixhawk 2.4.6 on qgoundcontrol, i can’t connect pixhawk on qgroundcontrol .I need your help .

thank you!

Have you tried restarting QGC and plugging the Pixhawk in and out?

And what are the LEDs on the Pixhawk doing after startup?