The prior process for holding mail has been considerably altered. Before, it was quite easy to take care of.
Now, if you have not already done so, you must create an account with the United States Postal Service and then go through a relatively easy few steps to get to the tab for Hold Mail. This entails creating a user name and a unique password. There will be identifying questions (Like: what is the name of your pet? For these kinds of questions, I follow the advice of security people and put something that is NOT your pet name because that is information that can be easily searched.)
This whole new process is for your protection. Make sure that you file your user name and password away so that you — and only you — can access it.