Fill Short Cut (Shift/F5) is not active when using Logi MX Keys keyboard

I’ve used defkey.com to track down shortcut issues.

What does the Shift + F5 keyboard shortcut? ‒ DefKey

I can’t say that it always helps. I have been unable to use the Alt Ctrl C shortcut for Canvas Size for a few years, for instance, and never managed to find what is stealing that shortcut.  In a way it has helped me out because I have to use Crop to add canvas, which I now really like.

Bumping this old thread for a random update. Unlock the F key row from the default media control settings that are shared on those keys. To do so, use the fn + ESC keys. The fn key should be to the right of the spacebar and between the alt/cmd and ctrl/opt keys. At least this is as it is on my Logo MX Keys S. Sadly, there are no  visual confirmations that pressing the two keys together have changed anything, but it worked for me. Just remember to toggle back and forth when you want to mute your speakers in three months ;)

I just happened upon this myself. Hopefully the bump might help others as this has been driving me crazy for a good year or so!!

First thing I'd test is to see if any F-key shortcuts work that don't have modifiers. Like try adding just a shortcut for the action to "F5" and see. If it works like that it could be a clue.

I'd also check if shortcuts F5 or Shift+F5 in other apps. If not it's possible the keyboard has some kind of feature that locks the function keys to instead use the 'secondary' function like setting brightness or whatever else the F-keys have as dual purpose. 

Apparently there are "keyboard tester" sites like this one which can show you which keys are getting pressed, so maybe you can see if the keys you expect are actually registering: https://keyboardchecker.com/

(Just realized this is an old post so hopefully you figured it out before my response 💀)