Sorry to keep posting, but I can't stop wondering why this display is not working.

Been going back over the thread and noticed a couple of things.

First, as far as I can tell (and I could be confused again!), the display has never been tried with the jumper and power both on position/pin 1.  The instruction page seems to indicate that this is the correct configuration to use.

Second, while looking at the pic of W1, I wondered if the jumper is surface mounted or has holes in the board.
If there are holes, did you use a wire for the jumper or just a blob of solder?
Don't mean to be rude, but the solder in the picture looks a little 'blobbish'.

Maybe just playing Devils advocate here, but I'm not convinced the new 5v cable will solve this issue.
The display driver was obviously working before, despite the low 5v.