Grunt isn't making changes when watching - css

Question

Grunt says waiting... but doesn't make changes to sass while watching. I have to run grunt on the command line every time I want it to run and change things. The thing I need it to update the most is the sass to css. But it's not working. Please help.
module.exports = function (grunt) {
grunt.initConfig({
pkg: grunt.file.readJSON('package.json'),
// package options
express: {
server: {
options: {
port: 3000,
hostname: 'localhost',
bases: 'public' // the 'public' folder for your project
}
}
},
jshint: {
options: {
jshintrc: '.jshintrc' // jshint config file
},
all: [
'Gruntfile.js',
'js/*.js'
]
},
concat: {
basic: {
src: [
'bower_components/jquery/dist/jquery.js',
'bower_components/foundation/js/foundation/foundation.js',
'dev/js/jquery.royalslider.custom.min.js',
'dev/js/royalslider.js',
'dev/js/megamenu_plugins.js',
'dev/js/megamenu.min.js',
'dev/js/megamenu.js',
'dev/js/app.js'
],
dest: 'dev/tmp/app.js'
},
extras: {
src: [
'bower_components/modernizr/modernizr.js'
],
dest: 'dev/tmp/modernizr.js'
}
},
sass: {
options: {
includePaths: ['bower_components/foundation/scss']
},
dist: {
options: {
outputStyle: 'compressed'
},
files: {
'public/build/css/app.min.css': 'dev/scss/app.scss'
}
}
},
imagemin: {
dynamic: {
files: [{
expand: true,
cwd: 'dev/img/',
src: ['**/*.{png,jpg,gif}'],
dest: 'public/build/img/'
}]
}
},
uglify: {
build: {
files: {
'public/build/js/modernizr.min.js': 'dev/tmp/modernizr.js',
'public/build/js/app.min.js': 'dev/tmp/app.js'
}
}
},
clean: {
dist: [
'tmp/**',
'public/build/img/**'
]
},
watch: {
grunt: {
files: ['Gruntfile.js']
},
css: {
files: ['scss/*.scss'],
tasks: ['newer:sass'],
options: {
spawn: false
}
},
js: {
files: [
'js/*.js'
],
tasks: ['newer:concat', 'newer:uglify'],
options: {
livereload: true,
atBegin: true
}
},
imagemin: {
files: [
'img/**'
],
tasks: ['newer:imagemin'],
options: {
livereload: true,
atBegin: true
}
}
}
});
// Load tasks
grunt.loadNpmTasks('grunt-sass');
grunt.loadNpmTasks('grunt-contrib-clean');
grunt.loadNpmTasks('grunt-contrib-jshint');
grunt.loadNpmTasks('grunt-contrib-concat');
grunt.loadNpmTasks('grunt-contrib-uglify');
grunt.loadNpmTasks('grunt-notify');
grunt.loadNpmTasks('grunt-contrib-watch');
grunt.loadNpmTasks('grunt-contrib-imagemin');
grunt.loadNpmTasks('grunt-express');
grunt.loadNpmTasks('grunt-newer');
// Register default tasks
grunt.registerTask('build', ['sass']);
grunt.registerTask('default', ['build','watch']);
}