Basically every organizers is responsible for providing invoices. We suggest you contact organizers for further help.
You can also click on the name of the organizer which displayed on the event pages. After you enter the organizer’s page, you can click on the button '' Connect with the organizer '' to get in touch with them.
You can refer to the following article to know more details about how to contact organizers
How can I contact organizers if I have questions about events?