It looks like you installed this module manually. In readme they wrote that
This module is intended to be installed using composer
Maybe you missed some dependency.
Another thing according to text under , do you see generated css file in this location after run deploy command ?
Run
php bin/magento setup:static-content:deploy
command and view files in the folder pub/static/frontend/Magento//en_US//css. CSS file is generated from test SCSS file.
3 it looks like your adapter don't work because class wasn't added. Is this module enabled? And magento:upgrade
- What is on line 51 in your Processor.php
What is on line 51 in your Processor.php
Maybe better try this is newer: https://github.com/splashlab/magento-2-sass-preprocessor