Chosen Solution
camera nikon coolpix p520 does not turn on change battery and it does not work
First check the battery. Is it charged? Is it healthy or old and dead? If the battery is OK take the camera to a service facility; you cannot fix the insides of cameras, unless you are a trained camera technician.
Talked to a Nikon repair guy: his simple answer … “it’s a contact issue” meaning the problem can be most likely solved with a soldering iron, reworking solder points one by one…
