EOS T3i not taking photos

[Phillylady]

1. It turns on
2. The lower right green dot, as viewed through the eye viewer, flashes off and on when I press the shutter button.  Nothing happens beyond that.
3. The button will not go half way down to focus, and it will not click to take a photo.  Therefore it is not focusing, or taking a photo.
4. None of the other settings will take a photo either,
5. EXCEPT when I put it into video. It will record video and SNAP A PHOTO while I am in video.
6. I have removed the battery and reseated it three times, it is fully charged and I've also tried using a 2nd battery. This is not the problem.

7. I have removed the photo card and reseated it 3 times.  It has tons of memory room left on it. 
8. I have removed the lens twice, and wiped the contacts (which look pristine as I normally never remove the lens).  
9. The camera is definitely set to AF.

I'm trying to figure out if some other setting on the camera inadvertently got shifted, but for the life of me I can't figure out what that would be. I'm not adventurous with the camera and just use the bare basics.

At the time that this happened it suddenly showed reluctance, I had to press down several times to finally get it to snap two final photos, and then it suddenly locked up completely.  It hasn't been banged, or knocked around, so I am mystified.

If you have any suggestions it would be really helpful if you could put them into layman's terms.  Pretty please. 

[ebiggs1]

"I'm trying to figure out if some other setting on the camera inadvertently got shifted, ..."

Whenever you have a situation where things don't work as you expected. do a camera reset.  This brings you back to a factory default status.  It is usually in the Tools menu and is Clear all settings.

Now that, that is done, Phillylady, go outside on a nice day. Sunny bright!  Set the T3i to the green square on the mode dial and the lens to AF on the AF/MF switch.  You can also use the P mode if you prefer but do not use any other mode at this point.  Green square or P only.  If all is well and the T3i worked as it should there is nothing wrong with the camera/lens combo.

Either way, if it worked or not get back and I can suggest some more stuff.