Problem with mijireh

I have a priority support ticket started with Mijireh, but after 36 hours (and 2 days prior to that with a non-priority support ticket)they still have not provided a fix so I though I would try here:

Everything works great, except when I click on the “Place Order” button I get the following error:

403 Forbidden
You don’t have permission to access /mijireh-secure-checkout/ on this server.

The URL in the browser address bar when this occurs is :
https://secure.mijireh.com/checkout/F3197A7E7C868C8D

But they maintain the error actually comes from my server when they redirect back to me to pick up the secure-checkout page. While this is plausible, the secure checkout page is available via curl or any web browser without issues. So there is nothing blocking it on my end according to my tests. Actually, according to the logs, I don’t even see a request from them but they maintain this is not likely and I am missing the log entries.

Anyone who has seen this error or can take an educated guess to help me out?

Thanks!

https://wordpress.org/plugins/woocommerce/