Hillary Clinton lost the youth vote by a landslide to Bernie Sanders during the Democratic Party's primary in 2016. Clinton lost to Sanders with those under the age of 45; with the biggest losses coming from college students. Basically, the Sanders campaign was better at connecting with the younger votes. In short, Hillary Clinton did lose the youth vote.
During her primary campaign, I believe Hillary focused on women's issues, which alienated a lot of youth. In contrast, Bernie Sanders played up starting a political revolution, which invigorated youth, and urged them to stand up for the things they believe in, which is a much stronger message and resonated more than Hillary's
The news recently reported that young people had voted for Bernie Sanders more than any other candidate. Hillary Clinton may have claimed that she was "fighting for you," but the youth weren't buying it. Clinton has a lot of support from key demographics such as Hispanics and the African-American community, but she isn't getting any help from what may be the most important demographic of all: young voters.
With her long history of engagement in matters relating to children and families, Hillary Clinton’s failure to inspire young people is notable and, at least initially, puzzling. Compared to Bernie Sanders, who is a youth magnet, she has failed to speak to the Millennial Generation or even the Generation Xers.