I have a Nikon D3100. The shutter does not work in many of the settings. In auto it will not work (when I hit the button it will pop the flash up and blink but not take the pic) but it does in Portrait, Landscape, and Sports. Nothing else works… Help!!
How are you focusing? Is it in focus? In AF-S mode, the default is that the shutter will not activate until the camera has found focus. Focus is indicated by the green dot at far left edge at bottom of viewfinder. If no green dot, then no focus, and no shutter.
Novices seem to like the wide focus modes where the camera just finds something (anything) and focuses on it. They can't be bothered with where or what that is.
It does depend your subject. A motionless subject or a fast flying bird, etc.
But for stationary subjects, the best results are single focus point in AF-S mode, so you can select where you want focus to be (at that point), and then it will focus on that point. You can move that single point around in the viewfinder if convenient (but the center point is often the strongest and best one). The shutter will work when the green dot says it has found focus. This is normally no issue.