Why couldn't Voldermort kill Harry Potter with Lucius Malfoy's wand?

I just finished watching the film Harry Potter and the Death Hallows:
Part 1. I don't know how the series will conclude as I haven't read
the books. Without spoiling anything, why couldn't Voldermort kill
Harry Potter with Lucius Malfoy's wand in the the beginning of the
film? If I need to continue watching to find out, then I'll accept
that as an answer. Thank you, kindly.