Cannot deserialize the JSON array (e.g. [1,2,3]) into type ‘ ‘ because type requires JSON object (e.g. {“name”:”value”}) to deserialize correctly

Your json string is wrapped within square brackets ([]), hence it is interpreted as array instead of single RetrieveMultipleResponse object. Therefore, you need to deserialize it to type collection of RetrieveMultipleResponse, for example :

var objResponse1 = 
    JsonConvert.DeserializeObject<List<RetrieveMultipleResponse>>(JsonStr);