Installation of pendant lite
You may have tried this already but your first step is to use a circuit tester to make sure you have power coming to the white and black wires.

If not, your next step is to walk backwards from the light to troubleshoot. If you made the correct connections at the light then go to the switch and verify that the switch is indeed wired to the line the light is on assuming you know the correct switch to that pendant.

Turn off the breaker to that circuit and unscrew the cover, you may have to also unscrew the switch to move it out of the way in order to see if the pendent wire is connected or not.

Chances are that the electrician has the wire in place but not actually wired to the switch. If it is wired to the switch. The next step would be to check the electrical panel to see if the breaker for this circuit is tripped and/or wired.

If all checks out then you can try to trace the circuit and hope to find the fault.