Dataset includes dynamic source - wont refresh in Power BI Service

I don't understand what I am doing wrong. Everything works in Power BI Desktop but it won't refresh in service. I followed the tutorial on Chris Webbs's blog but this issue persists. I have broken down parts of the URL as per this tutorial but it just won't refresh in service. Does anyone have any suggestions as to what else I can try to make this work?

Thanks

     apiURL = "https://something.comm.io",
     rel = "//livedata/data:search",
     headers = [Authorization="Basic myKey",#"Content-Type"="application/json", #"Accept"="application/json"],
     postData = Text.ToBinary("{my json data here}"}


            Source = Json.Document(Web.Contents(Url, [Headers=headers, Content = postData, RelativePath = rel, Query=[include = "session", siteCode = "1234567", pageIndex = p, pageSize = "500"] ]))