Why does Alfred require access to my Contacts?
In order for Alfred to be able to search your Contacts and present them in the results, you need to grant him access to them.
When you first install Alfred, you'll see a pop-up like this one. Click "OK" to allow access.
What if I clicked Don't Allow?
You can grant access by opening System Preferences to Security & Privacy. Go to the Privacy tab and tick the box next to "Alfred 3".
If you choose not to grant Alfred access to your Contacts, he'll continue to work just fine but won't be able to show Contacts in your search results (or when using the "email to" action, for example).