Json – While parsing string returned from API using JObject.Parse, getting invalid character encountered error

your best approach is to insert " before serializing.
P.S. I wrote fast, code can be refactored for better…

void Main()
{
    string json = "{"nbf":2024-04-17T16:28:14.509+0800, "iat":2024-04-17T16:28:14.509+0800, "iss":"https://google.com" }";
    json = FixJson(json);
    JsonSerializerSettings settings = new JsonSerializerSettings
    {
        ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
        Formatting = Newtonsoft.Json.Formatting.Indented
    };
    JsonConvert.DeserializeObject<Test>(json).Dump();
}

string FixJson(string j)
{
    j = ReplaceValue(j, "nbf", 28);
    j = ReplaceValue(j, "iat", 28);
    return j.ToString();
}

public string ReplaceValue(string s, string value, int len)
{
    var sb = new StringBuilder();
    int startposition = s.IndexOf(value)+5;
    sb.Append(s.Substring(0, startposition));
    sb.Append($""{s.Substring(startposition, len)}"");
    var last = s.Substring(startposition + len);
    sb.Append(last);
    return sb.ToString();
}

public class Test
{
    public DateTimeOffset nbf { get; set; }
    public DateTimeOffset iat { get; set; }
    public string iss { get; set; }

}