Using Windows 7 and 10 and IE 11, F-Secure Search works finefrom the F-Secure Search website. However, once theengine is activated, I can no longer search with thebox. I do not have that problem using Edge and Chromodo.
I decided to disable IE 11 on my Windows 10 personal computer and use Pale Moon as my default browser.
I will install Pale Moon as my default browser on my Windows 7 business computer, but I will not disable IE11 because some of my business software requires it for whatever reason. (I might need to enable IE11 on my personal computer; not sure if any of my personal software needs it.)