Why is my fragment shader not showing any colors?
After checking and rechecking my code over and over again. I finally made it work.
The problem was that I was creating the buffers and assigning locations to the position and the normals buffers

// Positions
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), 0);
// Normals
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), 0);


However in the vertex shader I was not setting the locations

#version 410

in vec4 vposition;
in vec3 vnormal;
...


So changing the previous code to

#version 410

layout(location = 0) in vec4 vposition;
layout(location = 1) in vec3 vnormal;


fixed the application.
Now, I am not really sure why this works, but I remember reading somewhere that OpenGL assigns locations as it sees best, so maybe in my code the location for the normal was not the same as the enabled vertex attrib array. I let someone more experienced clarify this.