What could be the reson that the software on the Discovery board does not start?

I have a STM32F407 discovery board on which the flashed software does not start when I connect it via the USB connector. The board is found by the PC (Windows, the folder is opened automatically), the LEDs on the ST-LINK light up, but the flashed software does not start.

This will only run when I have loaded the software on it again (I use the IAR workbench).