Symfony error The class XXX was not found in the chain configured namespaces XXX

This error message is indicating that the Symfony framework is unable to find a specific class within the namespaces that have been configured. This can be caused by a number of things, such as a typo in the class name or namespace, or a problem with the file system where the class is located.

To troubleshoot this issue, you should first ensure that the class name and namespace are spelled correctly, and that the class file is located in the correct directory. You should also check that the namespace has been properly imported in the file where the class is used.

If the class name and namespace are correct, it may be a problem with the autoloader. You should check that your autoloader is properly configured and that it is able to locate the class file.

In case you are using composer, you can try running composer dump-autoload to regenerate autoload files.

If none of these steps help, you should check the Symfony documentation or ask for help on the Symfony community forum for further assistance.