Trying to load sprite from Unity's Addressable but getting None Sprite instead

Question

So I'm trying to programmatically load Sprites into a struct I have and the code does not seem to be working as I expect. Here's what I have so far:

public class WeatherManager : Monobehaviour
{
    #region Variables

    private List<Weather> weatherList = new List<Weather>();

    #endregion

    ...

    public void Start()
    {
        InitialiseWeatherList();
    }

    ...

    private void InitialiseWeatherList()
    {
        if(weatherList.Count == 0)
        {
            weatherList.Add(new Weather(WeatherType.Cloudy, "Cloudy", "Weather_Cloudy"));
            weatherList.Add(new Weather(WeatherType.PartlyCloudy, "Partly Cloudy", "Weather_PartlyCloudy"));
            weatherList.Add(new Weather(WeatherType.Rainy, "Rainy", "Weather_Rainy"));
            weatherList.Add(new Weather(WeatherType.Snowing, "Snowing", "Weather_Snowing"));
            weatherList.Add(new Weather(WeatherType.Sunny, "Sunny", "Weather_Sunny"));
            weatherList.Add(new Weather(WeatherType.Thunderstorm, "Thunderstorm", "Weather_Thunderstorm"));
            
            StartCoroutine(LoadWeatherIcons());
        }
    }

    private IEnumerator LoadWeatherIcons()
    {
        foreach(Weather weather in weatherList)
        {
            yield return weather.LoadWeatherIcon();
            weather.SetWeatherIcon(weather.GetWeatherIcon());
        }

        foreach (Weather weather in weatherList)
        {
            if(weather.GetWeatherIcon() == null)
            {
                Debug.LogError($"Failed to load weather icon for {weather.GetWeatherName()}");
            }
        }
    }
}

My Weather struct is as follows:

public struct Weather
        {
            private WeatherType weatherType;
            private AssetReference weatherIconReference;
            private Sprite weatherIcon;
            private string weatherName;
            private string weatherIconName;

            public Weather(WeatherType weatherType, string weatherName, string weatherIconName)
            {
                this.weatherType = weatherType;
                this.weatherIconReference = null;
                this.weatherIcon = null;
                this.weatherName = weatherName;
                this.weatherIconName = weatherIconName;
            }

            public WeatherType GetWeatherType() { return weatherType; }

            public Sprite GetWeatherIcon() { return weatherIcon; }

            public string GetWeatherName() { return weatherName; }

            public string GetWeatherIconName() { return weatherIconName; }

            public void SetWeatherIcon(Sprite weatherIcon)
            {
                if(this.weatherIcon == null)
                {
                    this.weatherIcon = weatherIcon;
                }
                else
                {
                    Debug.LogError("Could not reassign weather icon.");
                }
            }

            public IEnumerator LoadWeatherIcon()
            {
                AsyncOperationHandle<Sprite> loadOperation = Addressables.LoadAssetAsync<Sprite>(weatherIconName);
                yield return loadOperation;

                if(loadOperation.Status == AsyncOperationStatus.Succeeded)
                {
                    weatherIcon = loadOperation.Result;
                }
                else
                {
                    Debug.LogError($"Failed to load weather icon for {weatherName}");
                }
            }
        }
    }

However, when I run my project, I get the following errors:

Failed to load weather icon for Cloudy
UnityEngine.Debug:LogError (object)
...

For all of the entries within the weatherList. I think my Addressables Group is set correctly for these assets. When I change the name of one of them, I get an error referring to the key not being correct, so it seems to be doing as it should.

However, when I look at my weatherList entries, I get Weather Icon None(Sprite) which tells me that the weather icon is not assigned as I expect it to be.

I've definitely not got something correct here but because this is a new system to me, I'm not sure where it's going wrong.

Thanks!