I have tried the above Troubleshooting steps, and still having issues.
I have found a work-around, but it’s ugly.
While editing a post in IE11 – hit the F12 button to bring up the Developer Tools.
Go to the Emulation Tab
Change the Document Mode to Edge
Change the User Agent String to Mozilla Firefox
After doing this, I can see the kitchen sink and TinyMCE. I need to do this every time I want to edit a post. Like I said…it’s ugly but it works.
I hope there is a patch coming soon.