Authentication Error

[aaxxios]

FirebaseAdmin: 3.4.0
.NET Version: 10

My firebase messaging stopped working all suddenly, no code changes, Firebase Messaging API enabled, Service Account credential is active.

Setup code in my service

var credential = CredentialFactory.FromFile<ServiceAccountCredential>(options.Value.FIREBASE_ADMIN_FILE);
_app = FirebaseApp.Create(new AppOptions()
{
    Credential = credential.ToGoogleCredential(),
});
_messaging = FirebaseMessaging.GetMessaging(_app);

When attempting to send a message, I now get the errors below:

FirebaseAdmin.Messaging.FirebaseMessagingException: Request is missing required authentication credential. Expected OAuth 2 access token, login cookie or other valid authentication credential. See https://developers.google.com/identity/sign-in/web/devconsole-project.

at FirebaseAdmin.Util.ErrorHandlingHttpClient`1.SendAndReadAsync(HttpRequestMessage request, CancellationToken cancellationToken)

at FirebaseAdmin.Util.ErrorHandlingHttpClient`1.SendAndDeserializeAsync[TResult](HttpRequestMessage request, CancellationToken cancellationToken)

at FirebaseAdmin.Messaging.FirebaseMessagingClient.SendAsync(Message message, Boolean dryRun, CancellationToken cancellationToken)

at FirebaseAdmin.Messaging.FirebaseMessaging.SendAsync(Message message, Boolean dryRun, CancellationToken cancellationToken)

at FirebaseAdmin.Messaging.FirebaseMessaging.SendAsync(Message message, CancellationToken cancellationToken)

at NoWow.EmailService.FirebaseClient.NotifyAsync(Guid userId, String token, String title, String body, Dictionary`2 data, CancellationToken cancellationToken) in /src/src/NoWow.EmailService/FirebaseClient.cs:line 67

To confirm my credentials is valid I did:

var credential = CredentialFactory.FromFile<ServiceAccountCredential>(options.Value.FIREBASE_ADMIN_FILE).ToGoogleCredential().CreateScoped(
    "https://www.googleapis.com/auth/firebase.messaging",
    "https://www.googleapis.com/auth/cloud-platform");
var accessTokenForRequestAsync = await credential.UnderlyingCredential.GetAccessTokenForRequestAsync();
Console.WriteLine("Access token: {0}", accessTokenForRequestAsync);

The above test returned an access token confirming my credentials are valid