Trying to demo PDF generation but getting an error message

Hi,

I am trying to demo your PDF generation tool, but I am getting this error.

"It seems there was an error on the server. Please try again"

My document has three tags: {{DNR}} {{LPOA}} {{CARELINE}}

My JSON data file content is

{
"DNR": "YES",
"LPOA": "NO",
"CARELINE": "YES"
}

I'm not really sure where I am going wrong...

Could someone kindly help?

Thank you