Hello, I have the same problem. I updated the shop version. The website closed. Then we restored backup but in extension control panel I have a session.php error. I can not install/uninstall & activate/deactivate the extensions. When I do it always shuts down the website. Shopware told that It looks like we are missing files from the vendor folder, they advise to completely replace this with a fresh copy. But how can I do that? I am not a developer but I have a plesk login. Is there a guide that I can do it step by step?