Even with the correct "bootloader version 240 mmi h43 download new," things can go wrong. Here are common fixes:
Firmware repositories often host multiple versions of the same bootloader. The "new" tag suggests that version 240 has recently replaced an older build (e.g., version 220 or 230) to patch a security vulnerability or a timeout bug during cold starts. bootloader version 240 mmi h43 download new
You should not download just any version; you specifically need the new bootloader 240 for the H43 platform. Here is why: Even with the correct "bootloader version 240 mmi
Using a terminal emulator (PuTTY or Screen): You should not download just any version; you
nand erase 0x0 0x200000 # Erase the first 2MB (Bootloader sector)
Wait for the "Erase Success" message.
With the device powered OFF:
Only if your device supports fastboot (rare for MMI boxes):
fastboot flash bootloader bootloader_240.img
fastboot flash mmi mmi_h43_new.img