Here's a good article describing 8 reasons why culture change can fail. 

In our experience, there is one stand out reason for failure. It is the only unequivocal reason why any culture change programme will fail; lack of CEO sponsorship. If you don't have the top person on board, and fully supportive of any changes, the escape route is too easy to take when the world becomes a messy, difficult and uncertain place to be. 

1. Bonus them and they will come

2. Silver bullet 

3. Understanding the importance of communication 

4. Speed kills change programmes 

5. Leader inconsistency and lack of congruence

6. Failure to move to a catalytic, coaching and facilitating leadership

7. Show a "light on the hill" not a "burning platform"

8. Toxicity in the top team 

Read Collingwood's blog '4 key leadership principles to manage change' here