<meta http-equiv="X-UA-Compatible" content="IE=edge">
is the first
<meta> tag on your page, otherwise IE may not respect it.
Alternatively, the problem may be that IE is using Enterprise Mode for this website:
- Your question mentioned that the console shows:
HTML1122: Internet Explorer is running in Enterprise Mode emulating IE8.
- If so you may need to disable enterprise mode (or like this) or turn it off for that website from the Tools menu in IE.
- However Enterprise Mode should in theory be overridden by the X-UA-Compatible tag, but IE might have a bug...