Unlike other forms in WordPress, Contact Form 7 doesn't automatically assign an id attribute to fields therefore you will have to manually add them.
if you need help with other forms please see the article about Google address autocomplete in WordPress by WPCube.
Add address autocomplete to an existing form
To add an id attribute to an existing form please follow these steps.
Go to Contact Forms and locate the form where you want to add address autocomplete.
Add id attribute just after the name attribute. For instance, id:some-id-name
Click Save button to save the changes
Then copy the newly added id and paste in Simple Address Autocomplete settings.
Click Save Changes to save it
Viola, your field has now address autocomplete functionality.
Add address autocomplete to a new form
While creating a new form in Contact Form 7, all you need to do is fill in the id attribute filed and add it Simple Address Autocomplete settings.
Follow these steps to create a new form with address field.
Add a new Text Field. It is important that you select TEXT field otherwise you may encounter errors
Click Insert Tag to add the field to the form.
Click Save to save the new form
Then copy and paste the id to Simple Address Autocomplete settings as shown above.