What could the cause of it be?

 

You probably have the Universal cable which does not work with EcuFlash 1.3x. I'm not sure why but version 1.29a will work.

This happened with my friend who has the Universal cable. I have the Tactrix cable specific for Mitsubishi so it works with any version.

 

That's weird, because I do have the Mitsubishi specific cable. I know this since I have the white connector that plugs in next to the OBD2 port.

 

The universal has that as well...

 

they're identical including the white connector (you need this for burning the rom). There're some different when you comparing the pins on the black connector.

When you setup EcuFlash and it's installing the driver for the cable, it'll say universal or mitsubushi only.