Did you have the red notification light flashing about once per second when trying to charge it?
This seems to be the status of mine too. It's drawing constant 50mA, but even after leaving it for 24 hours, it will not boot.
The rubber band trick is also NOT working for me. I tried several times, leaving it for over 24 hours for one attempt. So I'm guessing you had to disassemble and connect a bench PSU to the battery connector?