Reserve team not playing and very young players in U21national teams

I'm in my 3rd season as Koln and the only fixture my U23 team has played is the one against the senior team. I have never been prompted to enter my U23 into any competition like my U19 (which plays regularly). What can I do to fix this? I only have the top 2 divisions loaded, do I need to load more?

Also, is it me or there are some unrealistically young players in the U21 national setups? I got a 15 year old in the German U21 and a 17 year old in the Italian one. While in real life we have 24 year olds playing in the U21 teams.

Oh weird enough the players in U23 do get "league" matches in their stats, just the team has no fixtures.

I've been having the same problem with the Italian League

1- FC Köln II playing in Regionalliga West They playing the league matches but you're not seeing them because they're below the active level...

2- Sometimes younger players could get into U21 setups... IRL 23 years old players playing just for Olympic games or they allowed to play because they're in active zone for next euro U21 champs...

Simple answer is that you don't have enough leagues loaded. Although, for some clubs, even that may not be enough, if their 'B' team plays in a league below the level that SI allows play.

For the players in the U21 squads, it happens in real life as well. Romelu Lukaku has been playing in Belgium's U21 side and he's only 16, but they do need to be very good players to accomplish that. Additionally, I believe U21 teams are allowed 2 overage players or something of the sort.