Long time no see

I have updated one of my sites this weekend with the latest version. Wonderful work! Thank you. I am still missing the administrator language translation when using Joomla overrides and a fix for other language-related issues but I know that you are working on that.

What I realize is that the PDF certificate that is sent automatically by mail do not contain the image (only text). However when I open the certificate generated by the system on the Subscriptions page seems to be ok.
Any idea ion what can cause that?
Thank you!
Pascal