Thanks for your help. We finally resolved the issue! Our Magento is running under Windows IIS and there was a very bizarre rewrite rule issue with “app_code” in the URL.
After looking at the IIS logs we saw that one of the first requests to hit the website is:
It was returning a 404 error which is why I saw the error message on the iPhone.
If I bypassed the rewrite rules and tried:
And that works! So for now on our iPhone settings the URL is set to www.ourdomain.com/index.php/xmlconnect
So we’re back on track.