I'm trying to animate a character that I have created with blender 2.71, but something doesn't work well. As you can see from the screenshot, I have created the bones, I pressed Ctrl + P and then I have chosen the option 'With Automatic Weights'.
However, when I right click on a bone and I try to move it, the meshes of the character don't move; Only the bones do it. What am I doing wrong?
In Object Mode select all objects but the armature. Press Ctrl-J (join) .
Parenting with Automatic weights fails due to duplicated vertices. With the mesh selected enter Edit Mode select all A then press the Remove Doubles button from the left panel this removes > 3700 vertices.
You probably need to manually edit the middle part of the body because it is not connected. Or try to increase the limit when removing the doubles.
Note that this could also be done with a Mirror Modifier set to clipping.
After parenting with automatic weights your model requires weight painting. In your case I wouldn't recommend to use automatic weights because it adds much weights you only need to remove. Better paint it all manually from scratch.
I had a similar problem to the above. I had a part of my mesh that was weighted to a particular bone, but when I moved the bone, the mesh didn't move. After trying many of the steps listed above to no avail, I finally thought to glance at the bone's properties.
As it turns out, the deform property for that bone was disabled somehow. Once it was re-enabled, it worked as expected.
I ran into this problem as well. My issue was that my armature modifier had somehow had the "Vertex Groups" option turned off. Flipping it back on solved the problem for me.
I had this problem. However, with the new update, you find it in a new location.
EDIT MODE > select your model > toggle vertex selection > right click model > merge vertices > merge by distance > and in the bottom left panel select the distance.
I used 0.05m for a very dense photogram. 
I found the problem for me... I scaled, rotated and moved the mesh and the skeleton in object mode. Meaning the object center of both of them doesnt match. Set the position and rotation in object mode on all axis to 0 and set the scale to 1 (for both skeleton and mesh) Go to edit mode move your mesh and rig around and make everything fit. Now go back to object mode make sure position, rotaion and scale are still the same for mesh and skeleton... if so you should be able to parent your stuff properly.
Old post, but none of the above answers worked for me (2.82). I was having trouble with moving my mesh using my armature. I had already named them and finished weight painting. I had actually renamed the vertex groups while weight painting, but not renamed the bones as well. The fix was to rename all bones in the armature, and ensure that they matched the vertex group names that I had set while weight painting.
