Set me straight!

I connected my dash reverse light two days ago :)

Did u check the bulkhead connector..?
The reverse light wiring pass thru the firewall in the "Z" terminal of the bulkhead connector.
Engine side : the wire comes from the gearbox switch
Dashboard side : the wire goes to the dash light and in parallel to the body wiring connector, and then to the rear panel reverse lights.

If the "Z" terminal connection is bad, none of the three reversing lights will turn on, even with a good gearbox switch.