Dashboards stopped opening from application

I work for an elementary school.  We have a few dashboards that users access from a C# application and the application isn't opening the dashboards anymore.  No errors.  Just a blank page.  The application code has not changed, everything worked fine until yesterday.  I can still open/view the dashboards in Power BI with no problems (app.powerbi.com). 

I was thinking that perhaps the problem might have something to do with authentication, but I have no error to point me in the right direction.  I've pasted the code used to authenticate below (written by someone else), just it case that might be it.

I have no idea why the dashboards aren't displaying in our application all the sudden and I'm hoping someone here can point me in the correct direction. 

Thanks,

JMC

using Microsoft.PowerBI.Api.V2.Models;
using Microsoft.PowerBI.Api.V2;
using Microsoft.PowerBI.Security;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Microsoft.IdentityModel.Clients.ActiveDirectory;
using Microsoft.Rest;
using System.Threading.Tasks;

namespace CAGPAttendance
{
    public partial class CAGPAttendance : System.Web.UI.Page
    {
        private string Username = "Username";
        private string Password = "Password";
        private string ClientId = "ClientId";
        private string AuthorityUrl = "https://login.windows.net/common/oauth2/authorize";
        private string ResourceUrl = "https://analysis.windows.net/powerbi/api";
        protected string accessToken;

        protected void Page_Load(object sender, EventArgs e)
        {
            RegisterAsyncTask(new PageAsyncTask(ReadAsync));
        }

        protected async Task ReadAsync()
        {
            string task = await generateEmbedToken();
            accessToken = task;
        }


        async Task<string> generateEmbedToken()
        {
            // Create a user password cradentials.
            var credential = new UserPasswordCredential(Username, Password);

            // Authenticate using created credentials
            var authenticationContext = new AuthenticationContext(AuthorityUrl);
            var authenticationResult = await authenticationContext.AcquireTokenAsync(ResourceUrl, ClientId, credential);
            var tokenCredentials = new TokenCredentials(authenticationResult.AccessToken, "Bearer");

            // Initialize PowerBIClient with credentials
            var powerBIclient = new PowerBIClient(tokenCredentials);

            // BaseUri is the api endpoint, default is https://api.powerbi.com
            powerBIclient.BaseUri = new Uri("https://api.powerbi.com");

            try
            {
                // Create body where accessLevel = View, datasetId = "" by default
                var requestParameters = new GenerateTokenRequest("View", "");

                // Generate EmbedToken This function sends the POST message 
                // with all parameters and returns the token
                // first paramater is Group ID
                // second paramater is Report ID
                EmbedToken token = await powerBIclient.Reports.GenerateTokenInGroupAsync(
                    "removed",
                    "removed",
                    requestParameters);

                return token.Token;

            }
            catch (Exception exc)
            {
                return exc.ToString();
            }
        }
    }
}