Ok, you've opened multiple threads on the same topic, and not responded.
If it's not working you're evidently doing something wrong.
Make sure you've got the right pins, and the right AF mux settings, and that all the appropriate clocks are enabled.
We can't see any of the code you've changed, and we don't have your hardware configuration.
External Loaders are relatively complicated to code and debug. Perhaps you have other team members you can work with on this? Get some BSP level application code working for the read, erase and write, test and debug that first.
It's going to be very hard to diagnose and debug the situation based on the detail presented. Try harder..
