Feel like I'm adding loads of content so apologies if not needed!
Think the issue seems to be clubs who have an U18 squad but no staff allocated at the start of the save.
In my save, added some new managers.
Morton, who have U18 staff
- can place adverts.
- can allocate staff responsibilities
- can move players between senior and U18 squads.
Cove Rangers, who have a U18 squad but no staff
- can't place adverts,
- can't allocate responsibilities properly (see image)
- can move players to the senior squad, but cannot move them back.
Hope all this helps