If that's not already the issue (and it probably is ;p), see if a full battery drain followed by a full battery charge (i.e. well north of 12H on a wall charger) helps.
That's a fairly old device by now, so the battery may need some help to actually take and/or keep a charge
.
Which also means you don't necessarily need to be discouraged by the lack of sign of life, IIRC, the last time I had to revive mine to test something, it stayed dead for a couple of hours on the charger.