not a valid FCM registration token problem

I managed tu successfully send a FCM test message from Firebase console. However, when I try to send it from a console app using this code, I get an exception like:

"The registration token is not a valid FCM registration token":

public async static Task<string> SendByExample()
    {
        try
        {
            string credential_path = @"C:\IIII\XXXXXy\adminsdk.json";

           
            var app = FirebaseApp.Create(new AppOptions
            {
                ProjectId = "posmobxxx",
                Credential = GoogleCredential.FromFile(credential_path)
            }, "App name");

            var message = new Message
            {
                
                Data = new Dictionary<string, string>
        {
            { "additional_data", "a string" },
            { "another_data", "another string" }

        },

                // the notification itself
                Notification = new Notification
                {
                    Title = "a title",
                    Body = "a body",
                    ImageUrl = "link"
                },
                Token = "eYF7xxaLSbu0Zxxxx0bUO24lr:APxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
            };
            var firebaseMessagingInstance = FirebaseMessaging.GetMessaging(app);
            var response = await firebaseMessagingInstance.SendAsync(message).ConfigureAwait(false);

            return response;
        }
        catch (AggregateException ae)
        {
            string errors = "";
            foreach (Exception ex in ae.InnerExceptions)
            {
                errors += ex.Message + " " + System.Environment.NewLine;
            }
            return errors;
        } 
    }

The device token is the same as the one that I use for sending test message from Firebase console.