After publication of a new form the form is not automatically allocated to existing contacts.

The message class has to be changed for each contact to make sure that also existing contacts are shown with a new form. 

It's about a string field with the internal name MessageClass.

These are the steps to change the message class with EditContacts (Pro):

1. On the register Processing choose the action Replace and highlight in Selection an area that has to be worked on.
    
2. After that change to the register Settings and check the box All to ensure that all fields in the field list are shown.
    
3. Select the field Message Class from the field list. Now all available message classes in Outlook® are read out. This can last some seconds.
    
4. Go to Search and select the previous message class (default: IPM.Contact) and in the area Replace select the message class of your new form.
    
5. Click the preview button for a preview and the execute button to execute the change.

Next time you open an according contact he will be shown with the new form.