Your requirements could not be resolved to an installable set of packages. Problem 1 - jms/serializer-bundle[4.2.0, ..., 4.x-dev, 5.0.0-beta1, ..., 5.x-dev] require symfony/dependency-injection ^3.4 || ^4.0 || ^5.0 || ^6.0 -> found symfony/dependency-injection[v3.4.0-BETA1, ..., 3.4.x-dev, v4.0.0-BETA1, ..., 4.4.x-dev, v5.0.0-BETA1, ..., 5.4.x-dev, v6.0.0-BETA1, ..., 6.4.x-dev] but these were not loaded, likely because it conflicts with another require. - Root composer.json requires jms/serializer-bundle ^4.2 || ^5.0 -> satisfiable by jms/serializer-bundle[4.2.0, 4.x-dev, 5.0.0-beta1, ..., 5.x-dev].