Google have been making a recent push to get people to enable billing on their account when trying to register credentials, such as an API key for use with Google Maps.
Luckily if you already have a Google Cloud Platform account already, you can access your API keys – and create new ones – simply by following this link:
https://console.cloud.google.com/apis/credentials
Select a project from the top menu (or create a new one), and you’ll be able to create new API keys without handing over your card details – for now, at least… or until you hit your API limits!