Based on your previous posts, I'm guessing you are erasing the flash in your program which can cause the debugger to disconnect during startup. Some solutions here:
https://community.st.com/s/question/0D50X0000B8jTfw/stlink-error-devtargetnothalted
You can always connect with STM32CubeProgrammer (under reset if necessary) and erase the flash to get back to a working state.
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