I have the problem that when I start Fortnite, for example, my keyboard suddenly doesn't light up as I had set it to. It then lights up in a very ugly purple and when I press the Windows key and this menu with the taskbar is displayed, it lights up again as I have set it. It also flashes wildly back and forth as if it were set to equalizer when someone is dancing.
I've already tried
Reinstall -G-hub
Reinstall fortnite
hopefully that was well described and can help me.
Have you ever checked whether the Logitech software has created a special profile for Fortnite? If so, then all settings are to be made there. Then the keyboard should light up as indicated in the profile.
If the profile doesn't exist, I would recommend you create one manually and connect it to Fortnite.exe. Then the keyboard should always switch accordingly as soon as you run the exe.