Good evening Matt and welcome back!
Thank you for reaching out to us.
We are sorry to hear about the issue you are facing while allowing “guest” purchases.
I would love to help you with this topic.
I just ran a series of tests to try to reproduce your situation. Unfortunately I was not able to.
I believe the issue might rest with the WooCommerce – Autocomplete Orders version 1.1.4 by Serious Plugins plugin.
You see, for tickets to be sent, the order status has to be set to “complete”. Unfortunately, the way certain plugins achieve that does not yield the same results as actually marking the order as “complete” manually.
Could you temporarily deactivate this plugin and try to manually set a ticket order to “complete” to see if that works ?
As an alternative, the following snippet also sends the tickets automatically: https://docs.woocommerce.com/document/automatically-complete-orders/
Let me know if that helps.
Have a great day!
Geoff B.