Hey, I posted this on the comments for that example and was asked to post it here.
Apparently I'm not the only one with this issue.
I can't figure out why my cars.json file will load the single record, but once the config root is specified it blows up and tells me it can't read the json file. (STEP 8 In the Example) Any ideas? I've downloaded the completed xda file and compared my settings and all appears similar. I should note the complete xda file can't connect either, and just loads the blank grid.