Flutter Web应用集成AppCheck（企业版reCaptcha）失败求助

配置情况 #

• 已按Firebase App Check Flutter官方文档步骤配置，在Google Cloud控制台完成reCAPTCHA令牌配置，开启Disable domain verification选项并将localhost加入域名列表，页面提示的“完成密钥设置：请求评分”对Web应用不适用。
• 已在index.html中添加脚本：

<script src="https://www.gstatic.com/firebasejs/9.14.0/firebase-app-check.js"></script>

• AppCheck初始化代码：

WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp(options: DefaultFirebaseOptions.currentPlatform);
final appCheck = FirebaseAppCheck.instance;
print("we're also here");
appCheck.activate(
  webProvider: ReCaptchaV3Provider(appCheckToken),
);

• 已在Firebase控制台为Web应用完成AppCheck注册
  

问题现象 #

• 启用AppCheck强制校验后，应用无法连接Firebase服务
• AppCheck请求指标显示无已验证请求，所有新请求均标记为无效
  
• 应用请求返回400错误，网络请求详情：

Request URL:https://content-firebaseappcheck.googleapis.com/v1/projects/opincare-fbd30/apps/1:158357163473:web:33f42ed1a1c65248df2970:exchangeRecaptchaV3Token?key=AIzaSyCnQuY6rcVU4JTXH85GmBpYXNkd0K_cFpw
Request Method:POST
Status Code:400 Bad Request
Remote Address:172.217.17.138:443
Referrer Policy:strict-origin-when-cross-origin

• 调试控制台错误堆栈：

[2024-06-01T13:04:40.535Z]  @firebase/app-check:
[2024-06-01T13:04:40.537Z]  @firebase/app-check:
Error
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 299:10              
createErrorWithStack
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/core_patch.dart 355:28            _throw
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/core/errors.dart 120:5                                           throwWithStackTrace
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/async/zone.dart 1385:11                                          callback
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/async/schedule_microtask.dart 40:11                              _microtaskLoop
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/async/schedule_microtask.dart 49:5                               _startMicrotaskLoop  

内容的提问来源于stack exchange，提问作者Eight Rice