QR code is missing when mimetype is html

I’ve created an event, which sent an email to the token owner in case if the new token is created.
I’m using attach_qrcode options which are attaching a QR code to email, but if I change mimetype from plain to html there is no QR code in the attachment.

There are tons of reasons why this could happen.

Please learn to provide more information. Like your policies or log files. Take a few minutes to collect some information yourself. And think a bit.
And after that, state your problem and provide the information you have collected!

Don’t stop by crying, that something does not work as expected, without investigating at least a bit!
privacyIDEA is a complex tool that can work in thousands of different ways. So you need to get a bit more active here.
Thanks!

PS: Please take at least four minutes to think about, what could be a helpful information for someone to help you.