Measuring only 71 volts at light switch
Well as you said the light was not working in the first place. Replacing the switch apparently wasn't the problem. Your next step would be to investigate the light fixture itself. 

What type of light fixture is it? Flourescent, compact flourescent, LED?

When you say "71 volts across the circuit", do you mean across the switch? When it is on or off?

We need more information to help you.

Happy Sunday!