stm32h745 Mcu can work only when boot0 is high

Hi,

I am using dual core Stm32h745 mcu. I disabled the semaphore by commentig out. The mcu works after code download and reset with stlink. The mcu is able to restart with NRST pin.

My problem is : When I power off the board, that is custom made (not discovery), mcu code does not work whatever I try, like nrst. And stlink could not connect to the board.

The only way to connect stlink is when the board power up I made boot0 pin high, so that the board is able to connect stlink.

What could be the problem? The crystal I use may not work well.