FLStudio is open. Any monitor changes being made should be done while FLStudio is closed to avoid this issue.
Solution
In order to recover your off screen plugins you must perform a manual reset of your FL ...
FL synths and some external ones (Massive) but not on Kontakt or EWQLSO VST. I want to change the notes' colour so they can all play in the piano roll, but selecting multiple notes at once does not allow me to change ...