I had the same problem as roy, apparently. However, not snapping the middle snap of the back properly had left little craters in the gold contacts on the back, the springs on the phone side were OK.
Scraping and cleaning the contacts in the back with tuner spray was not enough. I slightly bent the tiny spring contacts on the phone side sideways (with a needle) so they now touch unharmed surface of the gold contacts in the back.
This did it.
If you need to copy this, be warned to be very cautious, as you can break the contacts...