Hi @MilanTandel ,
Thank you for your interest in the NXP MIMXRT product, I would like to provide service for you.
1. which board you are using?
2. which debugger you are using?
3. do you test the SDK project, whether that works or not?
4. normally, this is related to your flash unmatch the flashdriver, or your flash already contains the abnormal code which prevent the boot, you need to do the flash mass erase at first, you can enter the serial download mode, use the mcubootutility to erase it, then try to download the code again.
Wish it helps you!
Best Regards,
Kerry