Final answer:
The nurse should call the provider to determine whether the expired DNR prescription should be reinstated.
Step-by-step explanation:
In this situation, the nurse should take the action of calling the provider to determine whether the prescription should be immediately reinstated. Since the client's DNR prescription has expired and the client's condition is not stable, it is important to confirm the client's wishes regarding resuscitation. Assuming that the client does not want to be resuscitated without confirming could lead to potential complications and disregarding the client's current condition. By calling the provider, the nurse can seek guidance and ensure that the appropriate actions are taken based on the client's preferences.