Play some games and it go away on it's own.
Castle gate errors are caused when the gate is up, a ball goes by, and the switch after it gets missed.
There is a left and right gate. When you launch a ball into play it goes up above the lanes into the pop bumper and hits the closed left gate then bounces into the closed right gate.
Going into switch edge test won't erase this error.
Just play some games and it will right itself.
You can go into coil tests and check if the left or right gate lift. Since your game is new, I'm pretty sure the gates themselves are fine.
LTG : )