Stands a good chance its genuine then
Go to IHAD and download and try different versions of Dreamup, one of them is bound to connect to it.
Dreamup can be a bit funny at the best of times.
You are aware that with Dreamup, you have to start the software when the box is switched off. click on connect and then switch the box on. Providing you have set everything up correctly it should then connect to the box and install a bootloader to it to enable the flashing procedure to commence.
At least that's the way it works with my DM800HD through the RS232 Port. Never had to recover a DM800se with Dreamup so its just a guess since it uses USB and not the com ports.
Nano