I can't get my lunette to suction. This is only my second cycle, and I can get it in just fine, but once it's in it never seals. I know you're supposed to twist it, but I can't seem to get the hang of it. So then it leaks all day. And well, it doesn't leak a lot, but it's sort of annoying. When I take it out, I can just pull it out and don't have to break a seal, so that's another reason I think I'm doing something wrong. Any ideas/help?