Hi,
Thanks for reaching out!
This can be a bit tricky to set up. Let me share with you what I know.
Log into Google Could Platform.
Go to APIs & Services and select Maps JavaScript API.
Near the top you should see 3 tabs: Metrics, Quotas, Credentials.
Go to Quotas and make sure that your “Max loads per day” is set to unlimited.
As far as I know you can only set it to unlimited if you have a payment method assigned to it.
Now go to the Credentials tab where you should see your API key(s). Click on the one in question.
Under ‘Application restrictions’ select ‘None’.
Check if you have any restrictions under API restrictions, and make sure there are none there too.
Hope this helps, let me know.
Cheers,
Andras