Hi Alla,
When the device boot fails, can please run the debug GEL file provided here and report back the log that you see. Note that the device initialization is done by the AIS image so remove the device initialization GEL file before connecting to the DSP.
The debug GEL file will provide the error code, Value of Program counter that can help us debug the issue.
Other precautions that you can check for is that the bootloader uses L1D and L1P as full cache so no part of the initialization code should be placed in that space. Also check your application map file. We have noticed in the past that sometime the linker places some of the SYSBIOS code in external memory when it doesn`t find the appropriate section definition so look at the map file to ensure all of your application is in L2 and L3.
Regards,
Rahul
PS: Since you were able to boot non-OS code, I am assuming that the you are writing the boot image at the address 0x6000004 and that the NOR flash is connected to CS2 of EMIFA.