I'm migrating to OpenGL ES2 for one of my iOS projects, and I'm having trouble to get any geometry to render successfully. Here's where I'm setting up the VAO rendering:

void bindVAO(int vertexCount, struct Vertex* vertexData, GLushort* indexData, GLuint* vaoId, GLuint* indexId){

//generate the VAO & bind
glGenVertexArraysOES(1, vaoId);
glBindVertexArrayOES(*vaoId);

GLuint positionBufferId;

//generate the VBO & bind
glGenBuffers(1, &positionBufferId);
glBindBuffer(GL_ARRAY_BUFFER, positionBufferId);

//populate the buffer data
glBufferData(GL_ARRAY_BUFFER, vertexCount, vertexData, GL_STATIC_DRAW);

//size of verte position
GLsizei posTypeSize = sizeof(kPositionVertexType);

glVertexAttribPointer(kVertexPositionAttributeLocation, kVertexSize, kPositionVertexTypeEnum, GL_FALSE, sizeof(struct Vertex),  (void*)offsetof(struct Vertex, position));
glEnableVertexAttribArray(kVertexPositionAttributeLocation);

//create & bind index information
glGenBuffers(1, indexId);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, *indexId);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, vertexCount, indexData, GL_STATIC_DRAW);

//restore default state
glBindVertexArrayOES(0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
}

And here's the rendering step:

//bind the frame buffer for drawing
glBindFramebuffer(GL_FRAMEBUFFER, outputFrameBuffer);

glClear(GL_COLOR_BUFFER_BIT);

//use the shader program
glUseProgram(program);

glClearColor(0.4, 0.5, 0.6, 0.5);

float aspect = fabsf(320.0 / 480.0);
GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(65.0f), aspect, 0.1f, 100.0f);

GLKMatrix4 modelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -1.0f);

GLKMatrix4 mvpMatrix = GLKMatrix4Multiply(projectionMatrix, modelViewMatrix);


//glUniformMatrix4fv(projectionMatrixUniformLocation, 1, GL_FALSE, projectionMatrix.m);
glUniformMatrix4fv(modelViewMatrixUniformLocation, 1, GL_FALSE, mvpMatrix.m);

glBindVertexArrayOES(vaoId);
glDrawElements(GL_TRIANGLE_FAN, kVertexCount, GL_FLOAT, &indexId);

//bind the color buffer
glBindRenderbuffer(GL_RENDERBUFFER, colorRenderBuffer);
[context presentRenderbuffer:GL_RENDERBUFFER];

The screen is rendering the color passed to glClearColor correctly, but not the shape passed into bindVAO. Is my VAO being built correctly? Thanks!