On your site, I'm not getting a cross-origin error. What I'm seeing, instead, is a "referrer not allowed" error. This is usually caused by the API key being restricted to only a certain domain, but without specifying it fully.
Head for the Google API console:
https://console.cloud.google.com/apis/credentials
Take a look at your API key. The domain restriction, to cover all bases, should look like this:
*.example.com/*
example.com/*
If you change it, give it 15 minutes or so to "take" before testing again.