Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires sylius/paypal-plugin ^1.7.x-dev -> satisfiable by sylius/paypal-plugin[1.7.x-dev]. - sylius/paypal-plugin 1.7.x-dev requires sylius/sylius ~1.13.0 || ~1.14.x-dev -> found sylius/sylius[v1.13.0, ..., v1.13.8] but it conflicts with your root composer.json require (~1.14.0).