Finding fault can prevent both sides from seeking another way to solve a problem. As a last resort, go to an outside party for help. Then suggest ways to help. People who don't cooperate have different priorities. To make theirs the same as yours, show how you both will benefit by completing the task.
Some people resent following orders, so be subtle.
For example, post an itemized goal list. Let it go. If you find yourself nagging others too much, it may be time to evaluate your own duties. Recognize the time and effort colleagues put into the process.