What absolutely did not work for me (but that apparently works for other people based on frequency with which I encountered this solution) is just running AnyConnect through the Troubleshoot Compatibility wizard. That had zero effect for me.
What did work is this:
- Hit the Windows key and start typing "AnyConnect" to bring up AnyConnect in the search/launcher thingee (as I call it)
- Right-click on AnyConnect and choose "Open file location"
- Right-click on AnyConnect in Windows Explorer and choose "Properties"
- Click on the Compatibility tab
- Check the "Run this program in compatibility mode for" box and select "Windows 7" in the drop-down
- If you have a high-resolution display and AnyConnect looks fuzzy, and you care, you can also check the "Disable display scaling on high DPI settings" box
- Hit OK to save the changes.
- Reboot for good measure.
There have also been some previous issues with IE 11 updates breaking AnyConnect (yeah, wrap your head around that one) but those seem to have been resolved as long as you have your machine all patched up.