Symfony4登录报错：Authentication request处理失败问题求助

I'm currently learning Symfony while building a user account system with two roles: ADMIN_ROLE and USER_ROLE. No matter if I input the right username/password or completely wrong ones, I always get the same error message when trying to log in:

« Authentication request could not be processed due to a system problem. »

I’ve spent several days digging through the official Symfony docs and online troubleshooting resources, but I haven’t been able to fix this yet. Here’s what I’ve verified so far:

• Fixtures work perfectly: I can successfully populate user data into the database, and I can see those entries clearly in SQLyog
• I’ve tried deleting the entire database and rebuilding it from scratch multiple times, but the issue persists

Below are the relevant code files I’m using for this system. Let me know if you need any additional logs or details to help diagnose the problem!

security.yaml #

# Paste your security configuration here

UtilisateurFixtures.php #

// Paste your Fixture class code here

SecurityController.php #

// Paste your security controller code here

Utilisateur.php #

// Paste your User entity class code here

login.html.twig #

{# Paste your login template code here #}

UtilisateurRepository.php #

// Paste your User repository class code here

内容的提问来源于stack exchange，提问作者Michiyo1103