SOLVED! Trouble with U21 leagues in England

First, a bit of back story...

I've been working on a database that groups teams into the cities and nearby locations, combining their finances, board, staff, players, and wiping the history and records, sharing kits with new badges. Adding Irish, Northern Irish & Scottish teams into this too, and have the top 3 leagues in England populated (68 teams).

I've got all the first teams sorted and when testing the rules, I get a U21 division error. I've been pouring over the options for the last few hours and I cannot get passed this message.

As you can see the U21 Premiership has 20 teams, and they are all U21 Reserves of teams.

All I have changes is which teams are in the leagues, and the names.

Can anyone offer me any advice or suggestions please? I'm totally lost, and I'm sooooo close to being done and testing this DB.

Have attached the DB if you want to have a look.

Thanks in advance!

SOLVED

You need to edit the rules of the competition itself too.

Here:

And here: