After replacing harmonic balancer the vehicle will not start at all

Possibilities for these problem:

Make sure you lined all the fins up correctly?
One more thing  Did you use the old key or the one that came with the new harmonic balancer?
These can also make a bit of alignment difference to the balancer causing the same problem.


Another possibility can be crankshaft sensor got damaged while replacing harmonic balancer.
Either you install a new crankshaft