This happens to everyone.

It is possible that as your mind has more and more contact with DMT that you may need to increase your dose just a bit.  This is not the same as a classic tolerance such as with opiates.  It is a small adjustment in dosage that probably will only need to be done once or twice.

Try 45mgs next time.  Also there are just times when a breakthrough just won't happen no matter how much you smoke.  AGain it happens to all of us from time to time.