can't connect to STM32F407IGT6 on custom board

[tskn]

I have a custom board based on the STM32F407IGT6 and I'm having trouble connecting via ST-Link (v2 clone) using STM32CubeProgrammer. It seems st-link unable to find the target mcu. I checked all SWDIO, SWCLK, NRST, VDD, GND connections with a multimeter. I've used the ST-link with my another custom board that have STMF446RE and I can connect with no problem. BOOT0 pin is grounded and I can see NRST pin has 3.3V when board is connected with an external power supply. Custom board has only MCU soldered (and needed caps and resistors that connects to mcu). Board is powered externally and ST-link's 3.3V pin is also connected to target. I also have replaced MCU with a new one but this didn't changed anything.

What could be going wrong or I should check? I also attached schematics of the board if that helps.

[STTwo-32]

Hello @tskn and welcome to the ST Community.

Will using a Cloned version of the ST-Link V2, we can’t guarantee that it will work or not or if he is going to work on some use cases and not on others. So, my recommendation is to always use a genuine product.

Best Regards.

STTwo-32

[TDK]

BYPASS_REG and PDR_ON should not be left floating.

Probably also should not leave VREF+ floating either.

https://community.st.com/t5/stm32-mcus-products/stm32f446ze-not-booting/td-p/588722