Nikon D40 will not take a picture- flash will pop up but the shutter will not click. It doesn't matter what setting the camera is on.

SOURCE: Nikon D40 won't stay in remote mode

read manual ! you can change it up tp 15min.

Find in Custom Settings > "17 remote duration".
if it is not there change first in SETUP MENU>CSM/Setup menu from "simple" to "full"

SOURCE: problems taking pictures with nikon d40

The reasons for this could be one of the following, or even combinations of the following:

1) Low light. Especially if the AF assist lamp is set to "off"
2) Trying to focus on an even, single-color surface (e.g. a wall)
3) If you have set the camera to AF-C autofocus mode, it will keep on "hunting" with the slightest move of the subjects, causing lag. If you're not shooting (fast) moving subjects, make sure it's on AF-S or AF-A
4) If you have added a filter on the lens (e.g. a UV filter), remove it and see if it helps

SOURCE: Nikon D40 will not take a picture.

when you pusht o take a photo does it display an error on the top screen? make sure the lens is locked in including checking the ring on the lens next to the camera base.

SOURCE: faulty nikon d40

same thing has happened to me, only bottom half of the picture displayed and same message comes up. It looks like my best bet is to talk to Nikon about it. Thank you.

SOURCE: Nikon D40 will not flash

The lightning bolt icon in viewfinder blinks when flash is not ready, this can happen if flash doesnt pop up all the way, or if flash strobe tube is bad.