Flash Download failed - "Cortex-M0+"


I am currently working on keil, with NUCLEO L053R8 from STMicroelectronics, and I face this issue

          (Error: Flash Download failed  -  "Cortex-M0+")

since I have begun to use ST32CubeMX.

I have already tried to :

   - change com port,

   - change the nucleo board,

   - re-flash the binary file into the MCU, 

   -  flash with "BOOT0" high, 

but it has not change anything.

Maybe someone can help me.

Have a good day.

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