Woocommerce Emails breaking orders

Hello,

After a few days of oddly low sales activity, a customer called and informed us about difficulty in checking out. They would place and order and get an internal server error, and when they tried again, it would tell them an account already exists with that username. The order wasn’t going through, but the account was still being created. It turned out that no new customers could check out – only existing ones. Turning off automatic user registration was a temporary solution, but undesirable as it affects the Authorize.net CIM.

After updating both the gateway plugin and Woocommerce, as well as the theme, and deactivating a bunch of plugins in case any were interfering, it turned out that deactivating the new order and new account email that are automatically sent upon a new customer order fixed it. I had made sure that there were no saved theme templates and any snippets affecting email were off. Tried turning off our mailgun plugin too, but that did not suffice.

The problem is not with the general wp mail function, as others work just fine. Even a customer manager plugin meant to work with woocommerce that has a built-in emailer in the plugin works just fine using the base template. However, if I try to “re”send the new order confirmation, it doesn’t crash, but it is never sent. And if I open an order and try to select “Email invoice/order details to customer” I get the following error:

“The site is experiencing technical difficulties. Please check your site admin email inbox for instructions.”

Other emails in WP are working, but if I turn the WC emails on that would occur with a new order, no one new can place an order at all. I can’t figure out what caused woocommerce emails to sudden;y stop working, but the issue can be localized to this.