403 forbidden

Nobody has claimed this yet.

## Is it a security issue?
No
If you believe you have discovered a vulnerability or have an issue related to security, please **DO NOT** open a public issue. Instead, send us a mail to [dl_oss_dev@linecorp.com](mailto:dl_oss_dev@linecorp.com).

## What did you do?

> Please describe what you did before you encounter the issue.
I set up the config correctly, and re-did it again. The app was working one week ago but now when ii press login with line button in my app it takes me to line app but with forbidden 403 screen.

## What did you expect?
Get the token from the user.

## What happened actually?
I got a 403 page

## Your environment?
Dart SDK version: 3.1.3
flutter_line_sdk: ^2.3.6

## Sample project

```dark
LineSDK.instance.setup(dotEnv.LineID).then((_) {
print("LineSDK Prepared");
});

try {
final result =
await LineSDK.instance.login(scopes: ['profile', 'email', 'openid']);

final userId = result.userProfile!.userId;

return userId;
} catch (e) {
return Future.error('error');
}
```

Reproduce the 403 flow using Dart SDK 3.1.3 and flutter_line_sdk 2.3.6, starting with the shown LineSDK.instance.setup and login calls. Verify the LINE configuration and login scopes, then document the cause and the configuration or SDK change required for successful token retrieval.

Written by the indexing model from the issue text.