From reading the info it seems that if you use a browser it works but if you use the web viewer on an ipad it doesn't. I think the reason is that IOS does not use Java which is driving your authenticatin behind the scenes and so it probably won't work on IOS.
You can test this by NOT using the web viewer but by using an OPEN URL which should open Safari on IOS and see what happens. Start by creating a button with the OPEN URL and your http and see what happens. Hopefully when Safari opens it will work.
I've had the web viewer not respond in many instances in both Pro and Go where my regular browser on my laptop did and I think it is due to Java not running inside Filemaker Web Viewer, just a guess.
I also am guessing about Filemaker relying on Explorer for the browing although it might be Safari. Too lazy to remove all of my browsers to test this.
Thank you for your post.
Most of what "Jack Rodgers" has said is correct (Thank you!). To clear up any confusion, FileMaker Pro's Web Viewer is not a full web browser. FileMaker Pro uses the OS web kit to display web pages. Under Microsoft Windows, the web kit is modeled after Microsoft Internet Explorer, and under Apple's Mac OS, the web kit is modeled after Apple Safari. As "Jack Rodgers" suggested, use OPEN URL script step to launch the default web browser.