Error deserving JSON: The JSON value could not be converted to System.Collections.Generic.Ienumerable

Question

var stream = await response.Content.ReadAsStreamAsync();
var des = await JsonSerializer.DeserealizeAsync<IEnumerable<WorkingDaysDates>>(stream);

[JsonProperty(PropertyName = "RefDate3Before "]
public DateTime RefDate3Before { get; set;}

But when I test it, it returns the error: The JSON value could not be converted to System.Collections.Generic.Ienumerable