Hi,
First let me say that this is a great module, and it was a relief to find it (setting up tax calculations sounded daunting at first).
I have installed the taxcloud v1.4 module on zencart v1.3.9h and it is calculating tax correctly and adding it during the checkout process. Server is running PHP 5.2.17 and I double checked the SoapClient is installed.
The problem I'm having is when you click "confirm order" on the "main_page=checkout_confirmation" page, it loads the "main_page=checkout_process" page and it only says "
Setting order totals for taxcloud" at top left. That page doesn't redirect to the confirmation page, it just loads and stays. If I refresh on that page it loads the "main_page=shopping_cart" and the cart is empty.
Also, the confirmation email that gets sent for the order doesn't show any tax in the order totals, and the actual order total doesn't include the tax amount that was calculated on the checkout pages (checkout total doesn't match email confirmation total). I have tested many times with different payment/shipping methods and the result is always the same.
If more details are needed to help troubleshoot this problem please let me know. I can even set up a test account on my test site to see exactly what's happening if needed.