Tabular Editor "Unable to load Tabular Model"

Hi,

I want to get in on the use of Tabular Editor to author Power BI Datasets, and have followed the instructions provided by Matt Allington in his blog but I fall at first hurdle. When trying to open a PBIT file from within Tabular Editor, I am presented by this error message:

I've extracted the contents of the PBIT to look for a JSON file that references this, but there's nothing there. I've tried several different files. The reference to "culture" makes me assume it has something to do with locale settings - I'm in the UK - but don't know where or what I would change.

Any assistance gratefully received.