My PC doesn't recognize the VNM devices

The computer doesnt VNM device. but device manager shows:

-  STM32 BOOTLOADER

-  STM32 in DFU MODE

-  DFU in FS Mode

That indicates your VNM device is in Device firmware update which is used to upgrade firmware for the VNM devices.

 Base on each device, the DFU button can be a swtich, a button. with a button, it must be in low state to work as VNM device mode (high state mean DFU mode). with a switch, it must not be in DFU mode.

Change the state of the DFU button/switch and reconnect again. the PC should detect it :)