There are a lot of possibilities - I'd need a lot more detail to tell you what I think went wrong in your specific case.
Did you do the essay and IR sections on the practice tests (to the same level of seriousness that you did on the real test)? Did you stick to just the two 8-minute breaks? In short, did you take the practice test EXACTLY like it was real test day? If not, then you gave yourself artificial advantages / mental breaks that you didn't get on test day, and so that would affect you most during the final section, verbal.
Did you have timing issues? You can't see the data from the real test, but you might be able to see the trends in your practice test (even though the score was higher there). Use the below to analyze your most recent MGMAT CAT(s):
http://www.manhattangmat.com/blog/index ... ice-tests/Figure out what you think based on that analysis. Then come back here and tell us; we'll tell you whether we agree and advise you further. (Note: do share an analysis with us, not just the raw data. Part of getting better is developing your ability to analyze your results - figure out what they mean and what you think you should do about them!)
Finally, if you took our course or one of our Guided Self-Study packages, then you're eligible for a free Post-Exam Assessment (if you haven't done it already). This is a phone call with an instructor to figure out what happened on test day and come up with a plan to re-take the test. If this applies to you, please send an email to
studentservices@manhattangmat.com and request the Post-Exam Assessment.