"no STM32 target found" with ST-LINK V2 ISOL

[Kunal]

I purchased a new ST-LINK V2 ISOL debugger but whenever i connect it to my custom STSPIN32F0 board using SWD protocol (VCC, SDA,SCLK, GND), its showing no STM32 target found and error showing target voltage is too low but 3.3 V showing on the VCC pin.

[Tesla DeLorean]

How is the board powered?

Is it otherwise functional?

Show the salient portion of the schematic.

Make sure the ST-LINK/V2 has current firmware.

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[Kunal]

Please find my replies inline:

How is the board powered?

The board is powered through ac (220-240 V) which then goes through a full bridge and then through a LDO to supply 3.3 V on MCU (3.3 V is detected).

Is it otherwise functional?

Yes it was functional with earlier boards.

I cross checked the connections of the programming pins, they were soldered poorly. By again doing so, the connections became proper and the programming is functional now. Thanks for your valuable feedback.