I had a giggle. It seems we have disappointed the server. It's kindof ambiguous as a response too, I wonder what they intend it to mean.

It's suppposed to mean that the server doesn't support any of the formats the client specified in the Accept* headers. At least for the main Accept header, browsers typically include */* and even if they don't the server is better off just pushing whatever so yeah, would be interesting to know why they chose to return that particular error here.