STM32F769 Discovery DISCO Board USB HS Slave Interface Unrecognizable

[MXiao]

I used the ST USB device MSC program.The path is STM32Cube_FW_F7_V1.15.0\Projects\STM32F769I-Discovery\Applications\USB_Device\MSC_Standalone\MDK-ARM\Project.uvprojx.but it's still unrecognizable. I suspect there's a hardware problem.