hi I have a t4i canon I cant shoot in af. when I look into my canon peep hole it wont fire. only when i put it on full screen it focus and fire. when i look into the peep whole it has this green dot flash on in off. what can i do asap. and im shooting in M mode
You have provided so little info for us to form a mental picture of what your problem is...based on what you wrote...
1. Check the lens and make sure the focus button is on AF and not MF (most likely it's on AF since it works in liveview).
2. Liveview focus (on screen) and picture taking focus (via viewfinder or peep hole as you put it) is very different. Picture taking focus is more precise and therefore sometimes harder to achieve. This is what you probably were seeing.
3. The green dot flashing in the viewfinder signifies that focus is not achieved. When focus is not achieved, you cannot trip the shutter. That is what you were seeing.
4. You gave the impression that no matter what, focus cannot be achieved. Were you trying to take a picture in good light or poor light? Was your subject blending in with the background or there was good contrast? There is a point when focus is not possible (low light low contrast). Again see # 2. Picture via liveview might be possible but focus quality would be questionable. If you can't achieve auto-focus no matter what then something is seriously wrong. See # 1. You might have to send it in for repair or try a different lens.
5. If light is so poor you can't focus, switch the lens to MF (# 1) and manually focus yourself. If you are willing to use flash, pop it up...it will help the camera focus with the flash assist feature.
OK, not knowing the exact situation either, here goes. Set the camera to the green square. Set the lens to AF. Go outside, in daylight, and take a picture of a subject about 15 feet from the camera. Does auto focus work? If it does you have something set wrong for the other shot you are trying to get.