If you tried tapping the call button to make a phone call, but nothing happens, the quickest solution is to kill or close the Phoner app and then relaunch it again.
To kill or close the Phoner app:
- Open the Phoner app
- Kill the app, making sure that it is cleared from your phone's running apps
- Reopen the Phoner app
- Make a phone call and you should be able to dial out to your intended contact.