Dropix P3Pro firmware upgrade error

Hello, I’ve tried to upgrade firmware from 4.04 to 4.2.3 (Drotek pixhawk 3 pro) but I’m getting the following message:
Error: firmware image is too large for this board

this board have 2MB flash so I don’t understand why it telling me that…

Can you help me?

I tryed bootloader upgrade, but result in message “bootloader up to date”…

I don’t understand…