EV3 screen stuck at "Starting..." After I turn the device on, its screen is stuck at "starting..." for a long time. It hasn't change into the regular screen, and the light behind the button was still red (didn't become green). Is there a fix for this?
Try flashing the firmware. To get into firmware update mode, hold down the right button when turning the EV3 on. (You can also reset the EV3 without removing the battery by holding down the back and enter buttons for a few seconds.)

You can find much more detailed information on here.