USB-CAN Transceiver(STM32F0426U6) is not detected by the PC after a new .dfu file up-gradation

[RahulR]

I am using a USB-CAN Transceiver(Auvidea 70200), it consists a STM32F042C6C MCU. When I connect it with PC for the first time it was in "ST Device in DFU Mode". 

Using DfuSe Demo(v3.0.6) I tried to flash a .dfu file generated from a sample program of type .hex/.bin(for generating the .dfu file I used Dfu file manager software).

Then I successfully upgraded the .dfu file. Although I could not make it detected by the STM32CubeIDE tool, when I start debugging it was showing "No ST-Link Detected! Please connect ST-Link and restart the session".

Now the problem is my board is not even detected by the PC. What happened I don't know. Previously using device manager I could see that it was in "USB DFU Mode" How to make it work. I have added the device image also. Can anyone help me?

[Uwe Bonnes]

The board is not a stlink and it has no on-board debugger. You probably loaded some wrong application and now the bootloader is not entered any more. Probably the board has the boot0 pin exposed in some way. Change the state of boot0 to force bootloader entry with the next replug. Read AN2606 and the chip docs to find out how. For debugging, you probably need to connect a SWD debugger to the 4 golden vias beside the USB plug

[RahulR]

Thank you Uwe Bonnes for the reply. I understood that I loaded some wrong test application binary into the board. As you said I've checked both chip(STM32F042C6UX) docs and AN2606. I could not find any exposed pin for BOOT0 in order to forcefully make the board into bootloader mode.

When I checking the chip doc I found that PF11-BOOT0 and PB8-BOOT0 are allotted for Boot memory selection. Though I tried to connect BOOT0 pin with VDD by using an external wire. Still it has not been detected by the PC. Since the boot pins are very small and non availability of boot0 pin I am not sure whether the bootloader mode entry is success or not. I did not receive any datasheet for this product. Manufacture has not given me the response. That is making the hardware manipulation very difficult. Is there any other way that I can proceed? Can you please help me?