AFR gauge not working.

Let's back up a sec. You said all the wiring is the same as before. What changed with the installation of the new dash? Was this the ground for just the gauge, or was it also the ground for the AFR controller/sending unit? And what did you do while the ground was unhooked- ie, power up the dash, start the car, drive the car, etc?

AFR set ups are sensitive to grounding, especially the controllers. Touching the ground wire to the cage with all the power already on could definitely make the gauge and controller pretty, umm, unhappy to say the least. Or, turn them into bricks, in technical language. Digital components do not like voltage spikes or intermittent grounds. Is there a reset procedure for the controller? Have you cleaned all the ground terminals to bare metal and checked to make sure they're tight?