Resolving Errors When Generating Critical CSS via Console Command

The plugin requires the server to meet the Shopware 6 system requirements, with special attention to node and npm versions:

https://developer.shopware.com/docs/guides/installation/overview#system-requirements

Additional dependencies are required:

- libnss3

If you are experiencing errors during the generation of the critical CSS try installing any or all of the dependencies below:

- libpangocairo-1.0-0

- libx11-xcb1

- libxcomposite1

- libxcursor1

- libxdamage1

- libxi6

- libxtst6

- libcups2

- libxss1

- libxrandr2

- libgconf-2-4

- libasound2

- libatk1.0-0

- libgtk-3-0

run ``apt update -y && apt install -y libnss3 libpangocairo-1.0-0 libx11-xcb1 libxcomposite1 libxcursor1 libxdamage1 libxi6 libxtst6 libcups2 libxss1 libxrandr2 libgconf-2-4 libasound2 libatk1.0-0 libgtk-3-0`` to install all dependencies at once.

Steps by step procedure:

• Make sure your server meets the requirements specified in requirement list on the store page.
• Install and activate the plugin in your Shopware 6 installation – this can be done via Extensions > My Extensions > Apps.
• Open the plugin configuration using the three-dot menu.
• Configure your preferences
• Generate critical CSS using the "Generate critical CSS" button and keep the window open till the process has finished with a success notification.
• Clear the cache and navigate to the URLs returned in the notification.
• Once you have arrived on the storefront, open the Inspector by pressing the F12 key on your keyboard. 
• Verify the right amount of critical CSS has been generated by deleting the style file via the inspector of your browser, it should be just above the closing </body> tag.
• If some styles above the fold are missing, experiment by adjusting some configurations and regenerating the critical CSS.
• Enjoy better page speeds!