I followed the helpful guide on setting up your Google Maps API to narrow down the conflict that you seem to be having.
Based upon the error message in Chrome Dev Tools, it looks like you do not yet have an API key.
After you have created an API key, add it to WP-Admin dashboard » Events » Settings » API. Then refresh the page and see if that works.
When generating your API key, you should whitelist your domain(s) so owners of other domains cannot steal your API key’s usage.
We recommend that you include two urls like this:
*.example.com/*
*example.com/*
Please let me know if that helps. ?
Thanks,
Courtney