Plaid linktoken and expiration are null in live server

I tried running this locally, and it works perfectly fine, but on the live server, there's no exception thrown and it returns linktoken and exception null.

public async Task<CreateLinkTokenResult> GetPlaidLinkToken()
{
    var linkToken = await _client.CreateLinkToken(new CreateLinkTokenRequest()
    {
        ClientId = _clientId,
        Secret = _secret,
        User = new CreateLinkTokenRequest.UserInfo
        {
            ClientUserId = _userContext.CurrentUser.UserId,

        },
        CountryCodes = new[] { "US" },
        ClientName = "TestClient",
        Products = new[] { "transactions" }
    });
    return new CreateLinkTokenResult
    {
        Expiration = linkToken.Expiration,
        LinkToken = linkToken.LinkToken
    };
}

{
  "data": {
    "linkToken": null,
    "expiration": null
  },
  "exception": null,
  "errorMessage": "",
  "statusCode": 200
}

This is the response I get in the live server: