Hey, other than bad timing, I can't really think of what could be causing that. Who are you testing against? It doesn't work too well against Alpha, Pyrrha, Omega and Viola because of their small hitboxes.
Also, when you do the 3B-BE loop, you won't be getting an attack throw animation, it'll just lift them up over your head so that you can get the relaunch with c2B.