Cannot get it to work with .NET 9

[jh197033]

I have a simple test docker image built with the following compose file:

services:
libretranslate:
container_name: libretranslate
image: libretranslate/libretranslate:latest
restart: unless-stopped
ports:
- "5000:5000"
command: --api-keys --disable-web-ui --req-limit 0
environment:
- LT_API_KEYS_DB_PATH=/app/db/api_keys.db # Same result as db/api_keys.db or ./db/api_keys.db
volumes:
- libretranslate_api_keys:/app/db/api_keys.db

volumes:
libretranslate_api_keys:

In my .NET project I have added the nuget ref to LibreTranslate.Net and added using LibreTranslate.Net;

Then added the following code to call translate:

var libreTranslate = new LibreTranslate.Net.LibreTranslate("http://localhost:5000");
var englishText = "Hello World!";
var getSupportedLanguagesAsyncTask = libreTranslate.GetSupportedLanguagesAsync();
System.Threading.Tasks.Task.Run(() => getSupportedLanguagesAsyncTask).Wait();
var supportedLanguages = getSupportedLanguagesAsyncTask.Result;
Console.WriteLine(Newtonsoft.Json.JsonConvert.SerializeObject(supportedLanguages, Newtonsoft.Json.Formatting.Indented));
var TranslateAsyncTask = libreTranslate.TranslateAsync(new Translate()
{
ApiKey = "MySecretApiKey",
Source = LanguageCode.English,
Target = LanguageCode.Spanish,
Text = englishText
});

var spanishText = TranslateAsyncTask.Result; always returns null, am I missing some steps?