When I register for this event which is free for the sake of testing, I am sent to a receipt page with two buttons at the top: “Download PDF” and “Switch to Invoice”. When I click Download PDF the download is a completely blank pdf. The html receipt page looks complete. The PDF is blank.
It means the function to generate the PDF is likely throwing a fatal error, usually that happens when the PHP DOM module has not been installed on your server but without the error I’m just guessing.
You will usually have a section on your hosts control panel to view any errors being thrown, can you check there around the time you are downloading the PDF to see what (if any) error are being thrown?
The link for the event is here:
Can you either add a free ticket to that event, or create another with a free ticket so I can view it there (the Invoice/Receipt will still load for free tickets).