Battery door dosen't stay closed

I see this message at least 3 times, so it must be important.
Looks like a mechanical problem. But not having the camera in my own hands I have to do some educated guesses.
Could be something broke off. Could be a small chip of plastic or a very small piece of metal. Difficult to repair it yourself. But you also could look if there is something in the battery compartment that should not be there. Could be just a little bit of debris, that is lifting the battery, (not if the battery is behind the lock) or debris in the door, so you can't close the battery compartment complete, and it can't be locked.
If you can't find anything and it looks as if the battery compartment closes correct, and still you only can't lock the door, please visit your dealer or the Nikon service centre closest to you.

Push it closed with thumb .. hold closed..then slide forward

replace the body

Your batery is dead they don't like long period of staying discharging (If you 100% shure that your Nikon is working) The time of charge dosen't matter.

So other than the broken battery door (very common) it works just fine?

Well you could go and spend a fortune on another camera. Or you might decide that a few cents worth of sticky tape to hold the door closed is far better value.

I've fixed the same fault on similar Nikon models before by fashioning replacements for the broken plastic tab/loops using shaped short lengths of paper clip wire glued into carefully filed channels using epoxy resin (the designs vary, but Nikon keep making them of plastics with all the structural integrity of cheese!). Doing it that way makes a far neater and original-looking job of it and restores normal functionality.

on my camera battery door doesn't lock

www.thefotogeeks.com sells battery doors for the Nikon L20.

See fix 4 http://camerarepair.blogspot.com/2009/07/simple-fix-for-memory-card-locked-error.html?m=1

On ebay - NIKON COOLPIX 2200 3100 3200 Battery Latch Tab Repair

Happend to me after dropping the camera. Tape's good.