Follow the guide
here .
What have you reassembled exactly? Did you unplug any components on the board?
Can you still access Luma3DS menu and GodMode9?
@CraftyDuck100 The white led notification (not on the screen tho) is a sign that Luma3DS is missing from the sd card and/or from the ctrnand. So you should put the Luma3DS (boot.firm) manually to the root, and follow setting up Luma3DS ctrnand (on the guide above). And try again.