***Note: I wrote this in Aug 13, 2016. It solves most of the issues related to the Nikon Coolpix P600. Take note you need to find the "replacing the camera mount" solution to do the repair for the Nikon Coolpix P600. J Hess 04/2022 Most Helpful Answer Jerry Hess @mrjlh Posted: Aug 13, 2016 It is possible it is a small flex circuit that connects the power button module to the main circuit board is not connected correctly internally. If that is the case, it will need to be opened and the small flex circuit cable reset into its connector. If your camera is under warranty have it repaired through your dealer. If it is out of warranty like mine was I was able to fix it on my own. If you are mechanically inclined here's how I fixed it. I followed the disassembly procedure in "replacing the camera mount". You only need to get as far as step 9. The yellow flex circuits are inserted into a very delicate surface mounted PCB connectors. These micro connectors can not be repaired if broken. The entire PCB has to be...

You are quiet welcome. Wish I could edit the typos I made too. (just edited my solution)

I actually had to have the switch in my replaced by sending it out for repair due to warranty. But you could do it yourself if you have the part and the skills to do so. There is a great file showing how to take the camera apart some where on this site. Need to search for it.

You will need to reinsert all the flex circuits into their connectors inside the camera. One of them has become dislodged. If you don't have the skills your self to fix this by dissembling the camera yourself You'll need to send it out for repair. Otherwise You can read my answer at "Why does my camara keep changing selections" and start there.

OK I solved my "Own Problem" by fixing the camera myself. If you search on "Fix It" you will find "how to fix a "Nikon Cool Pix P600". It will show you how to take apart the camera and reassemble. It's been awhile but I think it was for replacing the camera mount . Anyway the instructions are very clear and easy to follow. I did find one small error and sent in the correction for it during the disassembly. Please be careful and handle the camera gently. What I discovered is the flex circuits within the camera easily become disengaged. They are held in place by a very small micro connector. This connector is very easily broken if you are not careful. There is a locking tab that is built into the connector. It lifts up and down. That tab has to be released, the flex circuit replaced securely and the tab re-locked into place. If the locking bar is broken you are screwed. The flex circuit is barely long enough for you to insert it into the connector and is easily dislodged. That is the "design" problem I sent...

It is possible it a small flex circuit that connects the power button module to the main circuit board is not connected correctly internally. If that is the case, it will need to be opened and the small flex circuit cable reset into its connector. If your camera is under warranty have it repaired through your dealer. If it is out of warranty like mine was I was able to fix it on my own. If you are mechanically inclined here's how I fixed it. I followed the disassembly procedure in "replacing the camera mount". You only need to get as far as step 9. The yellow flex circuits are inserted into a very delicate surface mounted PCB connectors. These micro connectors can not be repaired if broken. The entire PCB has to be replace. So take care when lifting the plastic connector lock that holds the flex circuit in place. What I found on my camera the flex circuit which goes to the "power switch module" was not inserted correctly or completely into the connector. It had come lose. I simply re-inserted the flex...

I too have a P600 with both the same problems. I had to send it in under warranty to get it repaired. They replaced a flex circuit board and switch. That worked for 6 months and now it will not turn on. Out of warranty now. I need to send it in or try to fix it myself. In looking at the "lens replacement" link I may try it myself. It appears that it maybe nothing more than a flex circuit that became disengaged. The quote for the last repair was almost $150 but that was covered under warranty. So I may need to send it in again. I do know that I will never buy a Nikon again. I expect quality with the Nikon name and Nikon has not delivered.