Hello,
If I use the test credit card which do not require the 3DSecure ; we do have the same error.
(you can test with the card "4000000000003055")
Because the payment intent system require an ajax call first, we do know that the Stripe plugin notification is working and can send a response.
But, when the order is confirmed, there is something which block the plugin to send it return data.
Thus, I do have the feeling that you have a plugin or maybe an email, which is triggered when the order is confirmed, and which stop the processing or clean the buffers.
One possible solution would be to edit the plugin and replace the content (that you can find twice) :
ob_start();
$this->modifyOrder($order_id, $this->payment_params->verified_status, true, true);
ob_end_clean();
By
while(ob_get_level())
ob_end_flush();
ob_start();
$this->modifyOrder($order_id, $this->payment_params->verified_status, true, true);
ob_end_clean();
It should flush the buffers that we "echo" just before and even of the "modifyOrder" (and the HikaShop triggers) stop the page processing, the content we just ask to display should be force to be displayed.
Regards,