AlfredCE

I don't believe that it makes any difference, but I'm not sure. Sorry. 

That's a good sign; it means that the display isn't bricked. Is this using a type A to micro-USB cable direct to the PC?
Is that the cable that came with the inverter, RJ-45 at one end, and D9 (RS-232) at the other? And are you plugging the two cables together?
It should be display -> cable that came with inverter -> USB to RS-232 adapter -> USB port of Windows computer.
That should be able to run Watchpower.
It's possible that the USB to RS-232 adapter isn't one that the Voltronic software works with. Check for a COM port appearing in the Windows Device Manager, and that the COM port is COM1 through COM9. I don't know about the display update tool, but early Axpert reflash tools would not work with COM10 or higher.
No, the reflash tools set the baud rate automatically. It actually starts at 2400 bps, and changes to 9600 bps as the reflash actually starts. I have no idea why they put a baud rate drop-down box there.
That looks OK, but as usual it doesn't say what the chipset is. The AEVA pages have suggested bands, and known good brands available from South Africa, but I don't know where you're from, and what may be available.
When trying to reflash, I assume that you're following the upload instructions, and are getting the UPG YES on the display? But you probably need to get it working with Watchpower via RS-232 first.
I also assume that you're plugging the cable that came with the inverter into the port nearest the PC/monitor icon.