The board I used is STM32G030. I don't know and I set the protection level to 2, so the board and debugger can't communicate. I want to go back to protection level 0, how do I do it?

[Danish1]

My understanding is that you cannot go back from level 2 to any other level. This is the "top level" of code-readout-protection in ST devices.

I know it's frustrating and an annoying waste of money, but your best bet is to buy a replacement board. Sorry.

[Tesla DeLorean]

How did you achieve this?

Don't use ST-LINK Utilities on newer products like G0 or C0 parts, the software has been deprecated for years.

Protection Level Two is not reversible, that's the point, even if you make a mistake, the silicon doesn't understand intent..

Experiential learners will simply need to learn and replace.