Good evening Henry and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
We are sorry to hear about the issues with the orders being cancelled at checkout. That must be very frustrating.
I would love to help you with this topic.
As a first troubleshooting step, could you please provide us with your complete system information in a private reply using the instructions found in the following link?
https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Best regards,
Geoff B.