I'm sort of still having this issue. The script failed for you because the username and password in the script I posted here are not valid.
Support has responded to my ticket and acknowledged there is a bug right now with how our site scripting operates and how the synthetic job emulates IE 10 and 11. The script works fine using Firefox or Chrome, so that's what we've done for now. I was told that a bug was created and would be resolved in a future release.