Has there been any change for this issue? I'm dealing with the same situation, playing as Scarborough Athletic. My U18s play matches, but despite my U21 side being in a league (the Humber Premier League, to be precise) and shown as such, they never have any matches. I have the setting in staff responsibilities set to "arrange a friendly every week", so even if the game thought the U21s were playing, my staff should still be scheduling friendlies, but they don't. I have to manually do so for every match.