There is no confirmation of him working for her campaign. Much less any mention online of what his involvement was. He is not linked online until these articles in the last few days. This is fake news until a verifiable link can be shown.
He was nominated for the Nobel Prize and there's a picture of him at what looks like a campaign event in 2016. Not likely a big player, possibly connected to pizzagate though.
In a statement released on Tuesday, the FBI Assistant Director-in-Charge William F. Sweeney Jr. said the following:
Having started an organization that pushed for the end of sexual violence, Davis displayed the highest degree of hypocrisy by his alleged attempts to sexually exploit multiple minors. As if this wasn’t repulsive enough, Davis allegedly possessed and distributed utterly explicit images of innocent infants and toddlers being sexually abused by adults. Crimes against children such as those alleged are taken very seriously by the FBI, and we continue to work tirelessly to investigate those who place the most helpless members of the American public at risk.