The first thing is does right click the Mcafee red shield show an activate option if so do so.
Second is your Pc behind a proxy server ie at a university this can block activation. Way to get past is log on outside the uni net and activate that way.
Third is did u or have you any other AV installed? If so remove it via its own removal tool.
Fourth is call Customer service they can assist.
Moving this to a more appropriate forum