add check

src/py/flwr/cli/utils.py

@@ -238,20 +238,21 @@ def try_obtain_cli_auth_plugin(
 
     config_path = get_user_auth_config_path(root_dir, federation)
 
-    # Load the config file if it exists
-    json_file: dict[str, Any] = {}
-    if config_path.exists():
-        with config_path.open("r", encoding="utf-8") as file:
-            json_file = json.load(file)
-    # This is the case when the user auth is not enabled
-    elif auth_type is None:
-        return None
-
     # Get the auth type from the config if not provided
+    # auth_type will be None for all CLI commands except login
     if auth_type is None:
-        if AUTH_TYPE not in json_file:
-            return None
-        auth_type = json_file[AUTH_TYPE]
+        try:
+            with config_path.open("r", encoding="utf-8") as file:
+                json_file = json.load(file)
+            auth_type = json_file[AUTH_TYPE]
+        except (FileNotFoundError, KeyError):
+            typer.secho(
+                "❌ Missing or invalid credentials for user authentication. "
+                "Please run `flwr login` to authenticate.",
+                fg=typer.colors.RED,
+                bold=True,
+            )
+            raise typer.Exit(code=1) from None
 
     # Retrieve auth plugin class and instantiate it
     try: