Authorize.net SIM Error

-- HikaShop version -- : 6.4.0
-- Joomla version -- : 6.1.0
-- PHP version -- : 8.4
-- Browser(s) name and version -- : Firefox 149.0.2
-- Error-message(debug-mod must be tuned on) -- : The reporting of this transaction to the Merchant has timed out. An e-mail has been sent to the merchant informing them of the error. The following is the result of the attempt to charge your credit card.

This transaction has been approved.

It is advisable for you to contact the merchant to verify that you will receive the product or service.

All of a sudden, I am having issues with the Authorize.net SIM. Customers are getting the "The reporting of this transaction to the Merchant has timed out..." error once they have successfully made their payment. It indicates that the merchant was sent an email about the error, but we have received no such emails.

• The order is properly created and the order creation email sent out to the customer and admin, reflecting "Awaiting Payment".
• The authorization transaction shows as successful in the Authorize.net console.
• The order shows appropriately as "Payment Confirmed" in the HikaShop admin console.
• The "Payment Confirmed" order status notification email is not sent out to the customer or admin.

We have not made any changes on the Authorize.net side.
The site was recently upgraded from Joomla 6.0.4 to 6.1.0.
I have checked the email overrides and have pretty much removed all customizations, except for a minor order title change. Even after that, the problem persists.

I purchased the Authorize.net JS plugin, but that has its own issues, which I reported is a separate forum post. So, right now I do not have a fully working credit card payment plugin.