System failed to generate the PDF document after PO cancel

Hello,

PO is approved. I cancel PO and system sends mail notification for supplier's contact.

I can see two attachments - Notification Details.html and PDF Document.htm.

After that I click at PDF Document.htm, error occurs:

System failed to generate the PDF document. Please contact your system administrator.

I found many notes for this error, but none about PO cancellation.

Setup looks correctly.

Can it be the problem of the cancelled message template?

Thank You.

Monika