How can I get my daughters ds lite to work again?

Only a month old? In this case, it should still be under waranty. On a new device, I suspect some fault that evaded the quality tests.

If you attempt ANY repair, it will void your waranty, so don't attempt any repair while it's still under waranty.

Bring it back to the dealer. He will replace or repair it.

Electro
January 2013