Important: Your map might look like it is working in the theme editor but in most cases will not display on your live store. Shopify's domains are whitelisted by Google so maps will always work in the theme editor.
Since June 2016 Google require an API key for you to embed a map on your site. There is a simple solution to this issue.
Setting up a Google API key is quite easy. You'll need a Google account and be logged in for this to work properly.
2. Click on the 'GET A KEY' button at the top right of the page.
3. In the popup that opens you need to name your project - something like your store name will do - agree to the terms and click the 'CREATE AND ENABLE API' button.
4. After the page has finished processing your request you will be presented with your API key. You can copy this quickly by clicking the copy icon.
5. Go back to your Shopify theme editor, open the Map section and paste the code into the Google Maps API key field. Don't forget to click the Save button at the bottom of the editor.
6. That's it! Your maps should now work- please check on your live store, not just in the Shopify theme editor. Shopify's domains are whitelisted by Google so will always work in the theme editor.