Error 500 (Joomla4, after trying to send certificates)

Hi, first of all thanks for EB - you have done great job, I love this component. But, when I try to send certificate from backend, the result is Error 500 (index.php?option=com_eventbooking&view=registrants).
Any idea how to solve will be most welcome. Using J4.
(I wanna use certificates as payment confirmation after check-in - by the way, isn´t there any way how to automatically send email to participant after the check-in status is changed, the same way as the email is generated and send after the status (=payment) is changed..?)
Thanks for any reply, Tomas   

Hi Tomas

What version of the extension you are using? If you are using latest version and see this error, please submit a support ticket sending us super admin account of your site and tell me ID of the record which I can send certificate to see this error

I will check to see why the issue happens and get it sorted

Tuan