In RT1064 EVK, I was able to program directly into external flash via J-link.
However, I cannot do the same in my custom board.
The difference is that my custom board is using kFLEXSPI_PortB1 instead of kFLEXSPI_PortA1.
Also, dqs pin is not used in my custom board. I had to change clock source as kFLEXSPI_ReadSampleClkLoopbackInternally instead of kFLEXSPI_ReadSampleClkLoopbackFromDqsPad.
I found i.MXRT1060 - SEGGER wiki page that FLEXSPIA_SS0_B is only supported?

https://kb.segger.com/i.MXRT1060
This means my custom board cannot be program/erase directly via J-link because I am using FLEXSPIB_SS0_B = GPIO_SD_B1_04?
My custom board mex file snippet is below:

Thanks,
Hyunwoo