i think you are using mendix 8, this error happened because the 'sourceStyleFolder' & 'deploymentStyleFolder' changed in Mendix 8. Go to your Gulpfile.js, and change the variable in the file as below: var sourceStyleFolder = 'theme/styles/web'; var deploymentStyleFolder = 'styles/web';
Not a solution to this specific error, but my advise would be to set up Calypso for the sass-parsing. It is way easier and in my experience, less errorprone. See this manual https://docs.mendix.com/howto8/front-end/calypso#1-introduction, which basically says: download, install, open, use.