.bg-clip-text missing -webkit-background-clip

[UmungoBungo]

I have been looking at the cropping to text example in the tailwindCSS docs.

If I copy the CSS from the tailwindCSS docs example to my website, the whole span receives the gradient, without clipping

TailwindCSS example;

Copying the classes into my website;

When I inspect this element, I've noticed that -webkit-background-clip is missing from the class

TailwindCSS example;

Copying the classes into my website;

If I add this in using devtools, it works as expected.

I double checked my package.json file, and I have the latest version of Tailwind.
"tailwindcss": "^1.9.1"

I also checked my tailwind.config.js and I'm not excluding any plugins

module.exports = {
  purge: [],
  theme: {
    extend: {
      boxShadow: {
        purple: '0 4px 14px 0 #805AD5',
      }
    },
    minWidth: {
      '0': '0%',
      '1/4': '25%',
      '1/2': '50%',
      '3/4': '75%',
      'full': '100%'
    }
  },
  variants: {
    opacity: ['group-hover'],
    scale: ['group-hover'],
    textColor: ['group-hover']
  },
  plugins: [],
}

Pretty confused, I must be missing something obvious?

[UmungoBungo]

fixed, needed
require('autoprefixer')
in postcss.config.js