Hi @cherub-chum,
Thank you for the feedback once again.
From the error I imagine you’ve executed composer install with --no-dev on the legacy folder, right?
To run the ./vendor/bin/pscss you need to run just with composer install, as the pscss is a dev dependency.
Please try running composer install on the legacy folder (under public/legacy) and after that re-running the pscss command also under public/legacy.
Please let me know if you still have issues after that.
Also, I think that the reference to composer install --no-dev in the developer guide, may be misleading.
I’ve added a PR for removing that from the documentation and to add a note explaining that pscss was added as dev dependency