[Flutter] authorization failed error when flutter pub get

I download a flutter project and want to run it. when run flutter pub get in command line, this error

Because eschool depends on win32 any which doesn't exist (authorization failed), version solving failed.
Insufficient permissions to the resource at the https://pub.dev package repository.
You can modify credentials using:
dart pub token add https://pub.dev


after run "dart pub token add https://pub.dev":

Enter secret token:
Requests to "https://pub.dev" will now be authenticated using the secret token.


what is secret token and https://pub.dev?

run "dart pub token add https://pub.dev" not solve my problem.your text

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