Issue Running Course On IE 11

Is anyone else developing courses for the U.S. federal government? If so, are you able to get it to run locally on a government computer using IE 11? I have developed/published a course and it runs fine for me on my computer with Chrome, Firefox, IE, and Edge. Two of my testers running a government computer cannot get the course to open in IE 11, the government's preferred web browser. I'm told they just get a spinning disc but no option to proceed or "allow blocked content". The course is published as HTML 5 only. Any thoughts or insights on what might be going on and how to resolve the problem are most appreciated!