Graph query works in console app, fails in azure function

I am querying Azure Active Directory using Microsoft.Graph. My method (shown below) works in a console app i created as a POC. When i try and use the method in an azure function it returns a HTTP 500 error, but does not give me any information to track down the issue.

The issue occurs on the below line:

IGraphServiceUsersCollectionPage usersPage = await graphClient
    .Users
    .Request()
    .Filter($"Department eq 'Information Technology'")
    .Select("Department,DisplayName,Mail,Id")
    .GetAsync();

The program hangs there for about 5 seconds and then postman shows a 500 internal error. Appreciate advice on how to troubleshoot or resolve this.

Full Method:

[FunctionName("Function1")]
public static async Task<IActionResult> Run(
    [HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] HttpRequest req,
    ILogger log)
{

    string tenantId = "xxxx-xxxx-xxxx-xxxx";
    string clientId = "xxxx-xxxx-xxxx-xxxx";
    string clientSecretValue = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";

    List<User> users = new List<User>();
    var scopes = new[] { "https://graph.microsoft.com/.default" };


    var clientSecretCredential = new ClientSecretCredential(
        tenantId, clientId, clientSecretValue);

    var graphClient = new GraphServiceClient(clientSecretCredential, scopes);


    IGraphServiceUsersCollectionPage usersPage = await graphClient
        .Users
        .Request()
        .Filter($"Department eq 'Information Technology'")
        .Select("Department,DisplayName,Mail,Id")
        .GetAsync();

    users.AddRange(usersPage.CurrentPage);

    return new OkObjectResult(users);
}

** I'm aware hard coding secrets is terrible practice, this was just a proof of concept before investing too much time.

UPDATE: The function is long running (taking about 3 minutes to run completely). It seems it is running correctly if i get its URL and execute it in a browser, it just does not run correctly in the "Code & Test feature" on the azure portal, functions blade