Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires sylius/sylius ~2.0.0 -> satisfiable by sylius/sylius[v2.0.0, v2.0.1, v2.0.2]. - sylius/sylius[v2.0.0, ..., v2.0.2] require symfony/webpack-encore-bundle ^2.2 -> found symfony/webpack-encore-bundle[v2.2.0] but it conflicts with your root composer.json require (^1.15).