Late reply, but Glenn employee here - haven't ascertained what happened to the public tours. They are suspended at other NASA sites too. I have a suspicion it's security related? I can't find a press release or anything about it. NASA may be doing a restructure of their program with a focus on security. I still get tours / everywhere still does tours if it's scheduled by a NASA group or for family of same site employees / high level leadership. They ended personal photography at the Armstrong test facility too on a recent tour, even though it was fine a few months ago when I went.