Hi.
I've had a good look through the logs, and actually everything looks fine, this doesn't seem to be hitting any FW issues. I'm afraid you've probably been unlucky and one of the electrical components has died preventing the backlight from operating.
If you put an image with some high contrast on it (e.g. on your windows backdrop), can you see anything if you shine a bright light on it?
DisplayLink only makes the video chip - we didn't manufacture the whole product you have, so I'm afraid there's not a lot more we can do - our bit seems to be working fine
I'm sorry you've had a bad experience, but there are more exciting products on the market than the U70 now.