Http error 403: Forbidden

[NidalShater]

I have tried to add the dependency to my flutter project but it keeps showing me that error
when I run flutter pub get

HTTP error 403: Forbidden

package:pub/src/http.dart 218:5 _ThrowingClient.send
===== asynchronous gap ===========================
package:http_throttle/http_throttle.dart 33:31 ThrottleClient.send
===== asynchronous gap ===========================

package:pub/src/source/hosted.dart 322:37 BoundHostedSource._download
package:pub/src/source/hosted.dart 217:13 BoundHostedSource.downloadToSystemCache

package:pub/src/entrypoint.dart 388:48 Entrypoint._get.

dart:async runZoned
package:pub/src/http.dart 272:10 withDependencyType

package:pub/src/entrypoint.dart 384:12 Entrypoint._get
dart:async Future.wait

package:pub/src/entrypoint.dart 245:18 Entrypoint.acquireDependencies
dart:async _completeOnAsyncReturn

package:pub/src/solver/version_solver.dart VersionSolver.solve
dart:async _completeOnAsyncReturn

package:pub/src/solver/version_solver.dart VersionSolver._result

This is an unexpected error. Please run

pub --trace '--verbosity=warning' get --no-precompile

and include the logs in an issue on https://github.com/dart-lang/pub/issues/new

pub get failed (server unavailable) -- attempting retry 9 in 64 seconds...

HTTP error 403: Forbidden

package:pub/src/http.dart 218:5 _ThrowingClient.send

===== asynchronous gap ===========================
package:http_throttle/http_throttle.dart 33:31 ThrottleClient.send

===== asynchronous gap ===========================
package:pub/src/source/hosted.dart 322:37 BoundHostedSource._download

package:pub/src/source/hosted.dart 217:13 BoundHostedSource.downloadToSystemCache
package:pub/src/entrypoint.dart 388:48 Entrypoint._get.

dart:async runZoned
package:pub/src/http.dart 272:10 withDependencyType
package:pub/src/entrypoint.dart 384:12 Entrypoint._get

dart:async Future.wait

package:pub/src/entrypoint.dart 245:18 Entrypoint.acquireDependencies
dart:async _completeOnAsyncReturn

package:pub/src/solver/version_solver.dart VersionSolver.solve
dart:async _completeOnAsyncReturn

package:pub/src/solver/version_solver.dart VersionSolver._result

This is an unexpected error. Please run

pub --trace '--verbosity=warning' get --no-precompile

and include the logs in an issue on https://github.com/dart-lang/pub/issues/new

pub get failed (server unavailable) -- attempting retry 10 in 64 seconds...

I'm using a proxy and I don't have this problem with other dependencies

What is the problem?