Ammeter wiring

You have to connect the black and red together so the power will flow to the rest of your car like it did before the amp meter was taken out.
Power just flows through it so removing the gauge severed that electrical connection to the rest of your car, and is probably why the key doesn't "work"

I know connecting a red and a black together doesn't seem right, but in the case of those 2 wires it has to be when the amp meter is removed.
Then you can continue the install of your new gauges.

Oops. plenty of replies already.