I just have this situation in the last distribution of CSA, I got a lot of people who are inactive for a year. I sent e-mails, team and individual, a couple of times. No one did not answer, at least negatively. I myself wondering what to do? That I should try some small gift, for example in the form of an e-book with useful advice. So I did, and maybe I have an answer :). We'll see if persistence pays off.