Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires guzzlehttp/guzzle ^8.0 -> satisfiable by guzzlehttp/guzzle[8.0.0]. - guzzlehttp/guzzle 8.0.0 requires guzzlehttp/psr7 ^3.0 -> found guzzlehttp/psr7[3.0.0] but it conflicts with your root composer.json require (^2.4.5). Problem 2 - Root composer.json requires hosmelq/sse ^0.1.0 -> satisfiable by hosmelq/sse[v0.1.0]. - hosmelq/sse v0.1.0 requires guzzlehttp/guzzle ^7.9 -> found guzzlehttp/guzzle[7.9.0, ..., 7.15.1] but it conflicts with your root composer.json require (^8.0).