Hi,
In our Sandbox, we offer both IE 10 and IE 11 support. PowerChart uses an embedded version of IE. Depending on what IE version is installed, PowerChart will pick up that version to use.
One thing that you may not have done is to include this html tag in all of the pages. That tag tells the document to render using the latest available version of IE.
<meta http-equiv="X-UA-Compatible" content="IE=edge">
Thanks,
Kol