Does it need an API key?

It needs an API key. In order to add it you should change the corresponding line in main.php to:

wp_enqueue_script('google-autocomplete', "https://maps.googleapis.com/maps/api/js?v=3&libraries=places&key=MY_API_KEY");

With this it works like a charm!

Maybe you could add a field in the backend in order for the user to enter and save the API key, and not mess with the code.

I added the API key, but the plugin is still throwing an error. I have upgraded to woocommerce 2.6. The address field is not editable and there is a small exclamation (error) icon at the left-top corner of the address field

I have the same problem, I have installed the plugin, and as there is no documentation or a good explenation, I had to search hours to see what needs to be done. I gererated the API key and placed it inside the main.php (for newbies like me: if you are wondering where this is, this file is located in /wp-content/plugins/checkout-address-suggestion-and-autocomplete-for-woocommerce/lib), but it does not work at all.

I am happy to provide a detailed documentation or a video to show how to install and configure this plugin, if the developer of this plugin let us know what is going wrong with it.

All the best, Happy New Year

thank you!!