Home grown players?

In my Game i have stupidly sold all but one of my players who were trained at the club who are over the age of 21 without realising, what happens if i attempt to register for the start of the new season without enough players trained at the club over the age of 21?

You will just have to register no player instead of homegrown ones. Homegrown players are optional but you cannot register another player in place of them. So if you have no homegrown players you need to register 4 less players if 4 is number of homegrown players to be registered.