Thanks @tatiang I think I have solved it now - I had added a field called type which is valid but I was putting an invalid value against it.
Thank you all for your help.
I may be posting a new thread on how to itterate through the JSON data and either and/or add it to a listview and database.
I found this post Best way to manage API data - #2 by hdawc but on trying this it has not worked for me.