Happens with my under 21 and under 18 team too. My under 21 are in a league, but my under 18 have not been in a league in ages even tho my youth level are 2 atm, soon to be 1.
In staff search, when I untick the choices in the include drop down menu ( interested staff for different teams and my own staff) then the staff search list are empty.
In all previous FMs I would see every staff that my club knew about, but now just empty.