Download the certificate template from here and then use this as an example and create the template from this, or simply edit the template present in that tip and then use it.
I have problems first with the generation of the certificate in PDF, when pressing the button "Generate Certificate" absolutely nothing happens.
https://ibb.co/zGmb49c
But when I click "View PDF HTML" this shows me the certificate correctly:
https://ibb.co/VtLTCtc
But then when assigning the certificate to a student and when the student wants to view their certificate, it doesn't show the background image, it only shows the text:
https://ibb.co/zR2TwvD