Newtons commonly need a soft reset when all power has been withdrawn and they have been left for a while. A soft reset works without wiping anything, whereas a hard reset - which you don't want at this stage - is intended to return to factory defaults, so is useful if the soft reset fails, or if the machine is full of stuff you don't want, or whatever.

Touch the tiny recessed button on the bottom with a pen/ paperclip briefly and see if it boots. It takes a few secs to begin.