I believe the answer provided by LazyInstantiation is incorrect and they are conflating DeviceTokens - https://developer.apple.com/documentation/usernotifications/registering_your_app_with_apns (unique token that identifies an app on a specific device) with ProviderTokens - https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/establishing_a_token-based_connection_to_apns (used for token-based authentication when making requests to APNs).
According to the APNs documentation, - https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/handling_notification_responses_from_apns the 429 response with error string 'TooManyProviderTokenUpdates' means
The provider’s authentication token is being updated too often. Update the authentication token no more than once every 20 minutes. Make sure you are not generating a new provider token for each request. The same provider token should be re-used (it should be refreshed before the 60 minute expiration but not more frequently than 20 minutes).