Gulp Autoprefixer Not Working

I know this question was asked a while back but I have stumbled upon a similar problem.

Here is how I resolved it:

1. Add browserlist entry to package.json:

{
"browserslist": [
    'last 2 versions', 
    'safari 5', 
    'ie6', 
    'ie7', 
    'ie 8',
    'ie 9', 
    'opera 12.1', 
    'ios 6', 
    'android 4'
  ]
}

2. Install autoprefixer

npm i --save-dev autoprefixer

3. Install postcss

npm i --save-dev postcss

4. Modify the pipe in gulpfile.js to be:

gulp.task('sass', function() {
    return gulp.src('scss/*.scss')
        .pipe(sass({errLogToConsole: true}))
        .pipe(postcss([autoprefixer()]))
        .pipe(minifycss())
        .pipe(gulp.dest(''))
        .pipe(plumber({
            errorHandler: onError
        }))
        .pipe(livereload(server));
});

This gulpfile:

var gulp = require('gulp');
var sass = require('gulp-sass');
var prefix = require('gulp-autoprefixer');
var minify = require('gulp-minify-css');
var plumber = require('gulp-plumber');

function onError(err) {
    console.log(err);
}

gulp.task('sass', function(){
    return gulp.src('src/style.scss')
        .pipe(sass())
        .pipe(prefix('last 2 versions'))
        .pipe(minify())
        .pipe(gulp.dest('css/'))
        .pipe(plumber({
            errorHandler: onError
        }))
});

With this scss:

body {
    opacity: .5;
    box-sizing: border-box;
    transform: scale(.5);
    display: flex;
}

Produces this output:

body{opacity:.5;box-sizing:border-box;-webkit-transform:scale(.5);-ms-transform:scale(.5);transform:scale(.5);display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex}

So, I'm not sure what I'm doing different exactly except that I list my browsers differently. But I assume you've tried removing those etc.

This should work, putting the browsers in an array, instead of as arguments:

.pipe(autoprefixer({
    overrideBrowserlist: ['last 2 version', 'safari 5', 'ie6', 'ie7', 'ie 8', 'ie 9', 'opera 12.1', 'ios 6', 'android 4']
})

and you can add cascade by setting it true or false cascade: false