Problem when i use GET acces to my API

Hi,
I want acces to my DATASET with API TEST Acces . I use the url that i have at my page :
https://my.api.mockaroo.com/users.json?key=678626e0

It appears the message: “{“error”:“undefined method `file_format’ for nil:NilClass”}”

What’s the problem, how i can resolve this.

Thank’s

can you share your Handler Script in API?