Appcompatv7 - v21 Navigation drawer not showing hamburger icon

Make sure that you're importing the correct drawer toggle.

When I imported the v4 version I had the arrow (below).

import android.support.v4.app.ActionBarDrawerToggle;

Changing it to this (below, v7) fixed my issue.

import android.support.v7.app.ActionBarDrawerToggle;

Make sure that you call

mDrawerToggle.syncState();

AFTER calling

getSupportActionBar().setDisplayHomeAsUpEnabled(true); 
getSupportActionBar().setHomeButtonEnabled(true); 

You need to call

mDrawerToggle.syncState();