Flutter AWS Cognito Token showing invalid signature - amazon-web-services

Question

I am stared developing a flutter project with AWS Cognito login features. In flutter, AWS Cognito login was working fine and I am getting the access token but when checking that in API or JWT its shows the error "Invalid Signature".
I add the below code for the AWS Cognito login features. I have installed the amplify_auth_cognito: '<1.0.0' in pubspec.yaml file to create the AWS Cognito login features in the app. Login codes working fine and perfectly but the token which returns from that code shows "Invalid Signature".
Future<String> _signIn(LoginData data) async {
try {
SignInResult res = await Amplify.Auth.signIn(
username: data.name,
password: data.password,
);
final resp = await Amplify.Auth.fetchAuthSession(
options: CognitoSessionOptions(getAWSCredentials: true),
);
if (resp.isSignedIn) {
final sess = resp as CognitoAuthSession;
print("TOKEN FROM THE COGNITO: ${sess.userPoolTokens.accessToken}");
}
setState(() {
isSignedIn = res.isSignedIn;
});
if (isSignedIn) {
_btnController.success();
AWSConfigurationHelper().getUserDetails();
Timer(Duration(seconds: 1), () {
_btnController.reset();
Navigator.pushReplacementNamed(context, DeviceList.routeName);
});
}
} on AuthError catch (e) {
Alert(
context: context,
type: AlertType.error,
title: "Login Failed",
desc: e.cause.toString(), //e.toString(),
).show();
_btnController.error();
Timer(Duration(seconds: 1), () {
_btnController.reset();
});
print(e.cause);
for (final exception in e.exceptionList) {
print(exception.exception);
print(exception.detail);
}
return 'Log In Error: ' + e.toString();
}}
My pubspec.yaml file screenshot was attached. In that file I am using amplify_auth_cognito: '<1.0.0' for the Cognito login.
I am new to this Flutter so I really need someone help to fix this problem. I have done the AWS Cognito Login features in iOS and web with the same AWS credentials but there I am not getting this type of "Invalid Signature" issue in the access token. Someone, please help me because I am not any good link where this type of issue has been discussed.
Thanks in advance