Reverse lights stopped working

Recently my back-up lights stopped working, both of them. I have tried the usual, check the bulb, check fuses and I have replaced the back-up light switch. None of these things proved successful. Any ideas what might be wrong?

I’d start looking for a wiring problem. Is current getting to the bulb sockets? Is the ground connection good? You’ll need a test light for this.

My daughter once had a car on which mice had chewed through some wires and knocked out the rear side marker lights.

No current is getting to the bulbs, but there is current at the switch. I’d just been hoping for something else since I’ve never tried to deal with wiring. No time like the present to learn! Thanks!